Time off calculations are quite complex, and there are a number of reasons why balances are wrong. Here are the most common reasons:
The employee start date is wrong: Air prorates time off based on start date. If the start date is after the holiday year start date the balance may be less than the total allowance.
The policy isn't configured properly: Go to Time off Settings then selecting Types and Rules. Is the total allowance right? Is the accrual schedule set up properly?
Note: Air won't update an employee's existing time off balance when you change the allowance of a policy. Only in the next accrual period (either next week, month, or year) will they receive the updated allowance.