when i top-up, how is my account expiration date calculated?

Topping-up your account extends your Cricket PAYGo account expiration date, which applies to all funds in your Cricket PAYGo account. When you top-up, your account expiration date is reset to 60 days from the date of your most recent top-up.  If you don't top-up before your account expiration date, you lose any funds remaining in your account.