It's okay not to understand everything about Math. I used to be a big enthusiast, even went to engineering school and loved the Math parts of it. But there are many, many, many topics I don't have the time or energy to grasp them, and I'm okay with that.

But yeah, nothing too magic about it. If you have one apple and you know that someone will give you another apple in 30 minutes, how many apples will you have in 45 minutes? That's right. 2 apples. Of course, predicting orbital trajectories is much more than that. But that's pretty much about it (lol!)