TimeTrex Time and Attendance

We are in US and use a time based shift differential and were told recently that overtime of 1.5 should be applied to the base hourly rate plus the shift differential. So if base wage is $8/hr and shift differential is $0.10/hr overtime for those employees should be $12.15 instead of $12/hr

Questions:
- is that interpretation of overtime correct in terms of US FLSA?
- how to do in TimeTrex as currently not working that way:
+ have premium policy pay formula defined by pay code
+ pay code type as Paid
+ pay formula for pay code is set for Flat Hourly Rate 0.10 (do we need to change to "Pay + Premium"?)

v12.6.5

Thanks

TimeTrex Professional edition has the ability to automatically calculate the proper FLSA overtime rate when employees get paid multiple rates of pay.