Half life is the time it takes for half of what was put in, to get out.

Simply put, in theory, Injecting 100mg with a half life of 7 days leaves you with 50mg after 7 days. half again (25mg) in 14 days and so on until it's out of your system in 4 to 6 weeks.

The following is oversimplified for illustration. If I'm injecting 100 mg of test every week with a half life of 1 week you'd get this:

1st week: 100
2nd week: 50 +100 = 150
3rd week 25 + 50 +100 = 175
4th week 12 + 25 + 50 +100 = 187
5th week 6 + 12 + 25 + 50 +100 = 193
6th week 3 + 6 + 12 + 25 + 50 +100 = 196 PEAK LEVEL
7th week 0 + 3 + 6 + 12 + 25 + 50 + 100 = 196
8th week 0 + 0 + 3 + 6 + 12 + 25 + 50 + 100 = 196

You should get some gains before the 4=6 weeks. However they should start peaking around 4-6 weeks.

10.5 days is the amount of time it takes your body to utilize the Testosterone with an Enethanate ester, for example a Doctor may give you 125mg of Test Eth as a TRT dose . The reason he gives 125mg is because that amount of Test Eth over the half life of the ester will mimic your bodies natural amount of free testosterone or there abouts.

Lets say your using Test Prop for example , it has a half life of 2 days give or take. Meaning it takes your body 2 days to utilize 100mg of test prop which is why you feel and see the results from test prop so much quicker.

The reason people say it takes Test Eth 4 weeks to kick is because your injecting every week at a dose higher than that of a trt dose, lets say 500mg . Every week you inject 500mg it is compounding in your body sending your free testosterone levels past that of "normal" week after week . Which when you finally get to 4 weeks of injecting your free testosterone levels should be sky high. Which in turn sends your body into performance mode, i.e. muscle gains, better muscular endurance , higher libido.

But also higher free test levels means in turn higher estrogen levels , that you battle with A.I's and such .

Just read read read you will get it.