Vacation Balance Calculation

MzWat

I wonder if someone can help me understand how wave is calculating vacation balances.

I have a FT employee whose vacation policy is set to “4% of hours are accrued each pay period”. She’s worked with us since 2018. Her vacation balance shows as 133 as of Jun 30, 2020. That seems way too high, so I pulled a Wage and Tax Report and here is the math using data from that report:
Worked 3925.46 hours since hire Jul 2018 (per report)
4% vacation is 157.02 hours (my math)
took 72 hours of vacation (per report)
Balance 85 hours of vacation (my math)

So why does wave have her vacation balance as 133? An overage of 48 hours. I know I can edit that number manually to be 85 if it is truly a mistake but I wonder if anyone has any insight as to why this might be out?

Might it be because this employee has been paid commissions and bonuses above her regular salary? Those amounts are captured in the wage & tax report but does that make a difference to the vacation accrual calc? Any other ideas?

Thank you!
Julia