This is an excellent result.
I understand that maybe you're just trolling (based on your reputation score), but I want to share the following information with you, to help you in case you are serious.
287.54 mg / 300 mg = 96% , which is well withing the +/-10% of label claim standard; therefore this is not "underdosed."

a lot of people don't even realize that the FDA standard is =/-10% and compounding pharmacies may follow a +/- 5% to +/-20% standard.

Also, keep in mind that the analytic testing results themselves have an error range and are a process run by humans; like with anything else, humans and measurements are not perfect so there are always error ranges/inconsistencies and tolerances in any measurements or processes.
Two analytic samples from the same exact batch may give slightly different results because the testing procedure itself also has some variance.

Therefore, if we consider the possible variance in production potency (+/- 10%, maybe even +/- 5% to +/- 20%) with the possible variance in the analytic results, the error may compound and give values that people wrongly call "bad" or " disappointing," and some even freak out about (because they may not understand, are ignorant, or just emotional and dramatic).

Overall, it seems that some people do not really understand these details and have developed some unrealistic expectations regarding analytic results.

US FDA and USP Potency Standards.

FDA-approved medications generally must contain active ingredients within +/- 10% of the labeled amount. For compounded preparations, the typical acceptable range is also +/- 10%, with a maximum, in some cases, of up to +/- 20%.

Based on United States Pharmacopeia (USP) standards, which guide pharmacy compounding practices, the information provided is generally accurate. [1, 2, 3]

Compounded Preparations (USP 795 & 797)
• Typical Range: The standard acceptable variability in potency for most compounded nonsterile (USP 795) and sterile (USP 797) preparations is +/- 10% of the labeled strength.
• Maximum Range: Depending on the stability of the ingredient, the specific dosage form, or if the ingredient is complex (such as some proteins), the acceptable range can extend up to +/- 20%.
• Other Ranges: For certain raw powders, potency requirements may be as tight as +/- 2%, while for others it may differ. [5, 6]
FDA-Approved Medications
• General Standards: FDA-approved manufactured drugs must adhere to strict stability and potency standards, typically requiring active ingredients to be within 90%–110% (+/- 10%) of the labeled amount, though some specific drug monographs may differ. [7, 8, 9, 10, 11]
Key Differences
• Compounded Drugs: Are not FDA-approved, meaning the FDA does not evaluate their safety, effectiveness, or quality before they are marketed, although they must be made using specific USP guidelines.
• Acceptable Variability: Because they are made one at a time to individual prescriptions, compounded drugs often have a slightly wider permitted variance (sometimes up to +/- 20%) compared to the strict, consistent manufacturing requirements of FDA-approved drugs. [6, 12, 13, 14, 15]

[1] https://allurepharm.com/understanding-compounding-pharmacies-requirement...
[2] https://burtsrx.com/what-is-liquid-medicine-compounding-pharmacies/
[3] https://www.linkedin.com/posts/farnamshime-tajhiz-b8800525a_pharmaceutic...
[4] https://www.arlok.com/news/CompoundedPrepLabeling"]ARL Bio Pharma | Labeling Compounded Preparations
[5] https://www.pccarx.com/Blog/notable-changes-in-the-new-usp-795
[6] https://www.arlok.com/sites/default/files/2018-03/Chemical%20Testing%20A...
[7] https://www.pharmacy.texas.gov/files_pdf/BN/Nov21/D.1.3.pdf
[8] https://www.excedr.com/blog/fda-drug-approval-process-guide
[9] https://www.ncbi.nlm.nih.gov/books/NBK562866/
[10] https://sonapharmacy.com/compounding-pharmacies-the-top-5-questions/
[11] https://med.stanford.edu/news/insights/2012/10/study-expiration-dates-ha...
[12] https://www.fda.gov/drugs/human-drug-compounding/human-drug-compounding-...
[13] https://www.pew.org/en/research-and-analysis/fact-sheets/2018/06/what-in...
[14] https://www.goodrx.com/drugs/medication-basics/compound-medications
[15] https://pmc.ncbi.nlm.nih.gov/articles/PMC10647869/

The United States Pharmacopeia (USP) establishes that the generally accepted potency range for most compounded and manufactured drug preparations is +/- 10% of the labeled amount, though this can vary from +/- 5% to +/- 20% depending on the specific monograph. These standards, often cited in FDA guidance and 21 CFR 211.192, ensure drug quality, purity, and potency. [1, 2, 3]

Key details regarding USP/FDA potency requirements:
• Standard Range: The common, accepted potency range is 90% –110% (+/- 10%) of the label claim.
• Variations: Potency requirements may be stricter (+/- 5% for potent analgesics) or wider (+/- 20% for some proteins) based on specific USP monographs.
• Regulatory Context: FDA 21 CFR 211.192 requires investigation of any batch that fails to meet these established specifications.
• Compounding: USP 795 & USP 797 standards for compounded preparations frequently reference the +/- 10% tolerance. [1, 2, 4, 5, 6]

[1] https://perfval.com/21-cfr-211-192-production-record-review/
[2] https://www.arlok.com/Potency-Testing-Benefits-and-Requirements
[3] https://qualitymatters.usp.org/what-letters-usp-mean-label-your-medicine
[4] https://www.fda.gov/drugs/electronic-drug-registration-and-listing-syste...
[5] https://www.pharmacytimes.com/view/2006-11-6068
[6] https://www.usp.org/sites/default/files/usp/document/FAQs/strength-stabi...

(NOTE: these are AI search and inquiry results, not my original work).