Wage type amount not Calculating Correctly

Hi Experts,

Please Need urgent reply. We create a wage type copying from a customizing wage type. But it not calculating any retro amount or not calculating actual value. For example I put data for wage type from 21.05.2013 - 31.12.9999 amount- 2000 and simulate payroll for pereod 02, 2013 amount calculate 2000 insted actual amount.

Thanks & Regards