Maybe this helps. Test is test, all the esters do is deliver it or break it down at different rates. This is why Sustanon has multiple esters to try to arrive at the smoothest yield in the body. Example being it is designed to be injected every 3 weeks and provide the most stable blood levels between injections. Single ester preps are not as stable i.e. the shorter the ester would spike earlier in the 3 weeks and then taper to nothing while a very long ester would not provide much initially and build in later. So that's the job of esters and why sustanon is blended that way. It's about long periods between injection and achieving the most stable blood levels between those points. Test is test, the attached ester just controls the timing.
Now knowing that, all these different esters have a weight and it's like a spectrum. The lighter esters are the fastest acting and the fastest to clear - so think prop here and even suspension which has no ester. As the ester gets longer into a cyp or enanthate or decanoate these esters weigh more and more while they become slower and slower acting.
So now you know that each ester has weight, the longer the ester the heavier it is, the longer the ester the longer the time, that test is test regardless of the ester attached, and that test has a constant weight. So when you have 100mg of pure suspension, you have more test molecules than in 100mg of proprionate (because the attached prop ester increases the total weight so less test per total weight to make room for the ester). This continues right down the scale as the esters get longer you get fewer total testosterone molecules in the same total mg weight. This is one of the reasons why people say that suspension or short esters are stronger, you just plain old have more molecules per mg.
Your Sustanon breaks out how much of the weight is actual testosterone. So if you have 176mg of test in there, it's the same as 176mg of suspension (which has no ester). So in reality you are not getting 250mg of test a week, you are getting 176mg every injection. They don't gross up the total mg to equalize test content, they simply weigh the whole substance ester and all which, when you hold mg constant between different compounds, means that the amount of test will varry due to the weight of whatever ester is attached.