Asset Depreciation calculation

Dear experts

we went live on 01/06/2012 and we started calculating the depreciation from period 06 and depreciation has calculated as normal for periods from 06 to 11, but when we have ran depr for period 12 system calculated the depreciation amount multiplied in 6 which means if the depreciation for period is 100, system calculated depr with 600 amount in period 12 only

i think system has calculated the depreciation from period 01 to 05 and post them in period 12 with the depreciation of 12

we use a multilevel method in depr key and we use a fixed percentage of depr for all period (straight line method)

please provide with your explanation of how that happened and how we can fix it

Regards

M.A.elsayed