Table Periods

Could anyone know what is the purpose of the "Table Periods" code "T" (UDC 06/DB) in the Source Calculation field (Alias DESQ) of the F069116 PDBA Master table?

What I am looking for actually is to retrieve the value of the last 4 pay periods worh of F0618 Timecard History, based on specific pay types that would be set up in the Basis of Calculation form, where the Method of Calculation (F069116.YCDEDM) would be equal to "%" and where the rate (Alias RTAM) would equal 100%. That supposes that somewhere I could enter the value of "4" for the calculation to limit the F0618 time card history retrieval to the last four pay periods only, and I don't know wherr I could possibly enter such value, providing of