burntpotato Dtle You can calculate it by youtself.
We know that fast pass is valid for a week, so If you have 12 fp in your account, then just
12:3=4 (We have 3 fp a day, so you got the first one 4 days ago)
7-4=3 (the first 3 fp will expire in three days, so you need to use them within 3 days)
3*7=21 the maximum amount you can have in your account, so If you have 21 fp then
21:3-7=0 you need to use 3 fp today because tomorrow they will expire already.
I hope it will help somehow.
Marry Xmas and Happy NY!