/458 and /460 cal Problem

Dear Experts,

i am facing a problem in tax calculation of one employee in my organization

all WT of tax is calculating correct but /458-Net tax payable is also correct

/460 is /458 divided by /401+1

here /401 is 1

so according to that it has to calculate , but it is not doing like that for one employee

actually /458 is 17000

then /460 has to be 17000/1+1=8500

but system is giving 17000 as /460

please tell me why system is calculating that logic..

please advice..thanks in advance

Regards

sajid