@dajee–It’s a really bad idea to send corrections regarding activities hours unless you’ve made an EGREGIOUS error (e.g., you wrote down that you deliver pizza 3 hours/week when it’s really 30 … or vice versa).
Every time a student sends an activities-hours correction, he or she is also sending a message that suggests, “I couldn’t be bothered doing this carefully the first time so now I want YOU to spend extra time on me.”
Occasionally it’s necessary to send this kind of correction anyway, but I typically warn students to avoid doing so unless the situation feels urgent. And, from what you’ve said about your own situation, it isn’t.
Don’t worry about putting down your intended job hours and weeks. This is a very confusing part of the application and the college folks will definitely understand what you mean.
As for the places where you put 2 hours when you should have put 10, I recommend that you leave it alone. You’ll do more harm than good by sending a correction, as explained above. BUT … if you end up having an interview for this college, then it’s fine to explain the mix-up to the interviewer and ask that the correction is added to your file.