Inception to Date DBA

I am trying to set up a Benefit that should begin calculating $.33 per hour (current period) after the employee reaches 600 hours worked.  The two available Table Methods HD & HP don't calculate properly for what I need.  I do have some "Z" Table Methods but they don't seem to recognize the hours listed in the Basis column in PDBA History by payroll month - as I loaded, through interim checks, YTD hours for all affected employees.  Or does "inception to date" have a different meaning in JDE?  Do I need to set up a special DBA to calculate up to 600