Those results don't seem too surprising to me.
I'll try and find a study I found that dealt with this issue. It placed the individual variation in Total T as +/- 150 ng/dl measurements on the same day each week. I think it was 100 mg/weekly in 1 shot but in 3 weeks your results could be 500,800, 620, or so, on day 5 (or whatever day). So over a range of 300 ng/dl on the same 100 mg/wk dose.
It doesn't seem too surprising really - if you add up all the ng/dl in the 5 liters of blood you have, it adds up to less than a mg, and daily production's 3 mg - 10 mg in 90% of people, so the blood levels don't tell the whole story.
I went looking for the story after I already suspected it. Personally, I don't really believe the "we're all different" adage that goes around the boards, in the broad sense that it's used. I think there's this variation, different people test different days, and many have other issues that aren't T related. Very few natural males make >100 mg/wk Test Cyp equivalent, so for T related issues, that should set most anyone straight, imo. If that doesn't make someone feel better than the emphasis should shift to other systems or subsystems.
Personally, I wouldn't worry about it if the dose is reasonable and your other biological markers are okay.
