Table Method - by Percentage of Regular Salary

Dear Experts!!!

In the payroll system, we accrue 2.5 days which is 20 hours flat for 30 or 31 day which employee works.
For Example,  
30 days = 240 hours = Accrue 20 hours.
So if the employee avails 1 day of Unpaid leave system calculates are,
29 days = 232 hours = 19.25 hours
 
When we apply a caclulation table for accrual,
 
0 - 6 months = 0 hours
6.1 - 12 months = 2days
12.1 - 999999 months = 2.5 days
 
I am not able to reduce the accrual days in case of unpaid leave. In all cases it is accring flat number.
 
Is there a table method to setup the percentage(%) of base pay,
 
0 - 6 months = 0%
6.1 - 12 months = .0667%
12.1 - 999999months = .0834%

Thanks in Advance,