There is going to be a lot of factors that will contribute to weight gain:
-Caloric surplus
-Increased glycogen storage (from the test)
-Increased estrogen levels (from the test)
-Gains in muscle
The caloric surplus alone of 500 cals will lead to about 10-12 lbs after a few months. The test will allow more glycogen to be stored within the muscles as well, so add a few lbs there. Estrogen levels (even with an AI) will be high from 500mg/week which will contribute to some water retention and possibly some fat (especially when in a caloric surplus). Another couple lbs in lean mass can be expected as well.
So as you can see, once all these factors are added up, it is easy to expect a 20 lb gain from this cycle, especially when your goal is to bulk.