Time track shift maintenance not calculating overtime correctly.

I have a shift set up for our Regular day to day and it is set to calculate overtime at anything over 40 hours for the week.  During a holiday week we pay overtime on anything over 8 hours a day, so I set up a separate shift in shift maintenance and have changed the shift code on time entered to reflect this for the week but it still won't calculate anything except the 40 hours plus for the week.  Any suggestions?