$0.00 overtime rate

My employer doesn't pay me an overtime wage, instead I get time in lieu. I use the overtime feature to track how many extra hours I work to then submit to my employer, but the lowest I can set my overtime rate to is 1.0, meaning the total earnings in the app is more than my payslip. It would be ideal to set the overtime rate to 0.0 so my earnings still accurately reflect my payslip, while still being able to track overtime hours.