Thanks. I'm glad you are enjoying the simulator.
I'm not quite sure how to answer your question. The simulator works with sublevels, meaning that it relies on you to have a decent estimate of how much training your player has received since his last pop. So, it assumes the pop will happen at x.0. But if you don't have an estimate of sublevel to put into the simulator, you might pop at what seems like x.5 because you have un-input sublevels on your player.
EXAMPLE: An 18yo 6'0" player is input as having 5 OD. This means he could be 5-5.99. He gets trained twice in Pressure (PG). The TS shows that he'll get to 6.2 OD, indicating 1 pop. But this means he could be anywhere from 6.2-7.19. So he might have popped twice.
But say you have trained the same player enough times to know that their sublevel is 7.2-7.3 OD and so you input '7.2' for OD. After the same training you'll know he'll be between 8.4-8.5 OD.
Clear as mud?