Net pay issue

Hello All

We are running payroll. IT0008 is maintained as US$ 752.

Payslip shows as

Basic Pay 752

Basic Pay 752

Basic Pay 752

Deduction 59

System is running retro 2 period, 1 period regular salary but net pay 2949 ( ie 752*4 - 59 = 2949)

Please let me what went wrong, why basic pay 752 is multiplied by 4 times ?

Please let us know in detail