How do we enter additional state withholding for Mississippi in F06017?

We are trying to enter additional state withholding for an employee who lives and works in Mississippi.

The issue is that for Mississippi, the user enters in F06017 the following for each employee who works in Mississippi:

FT01=X

TARO=25

PTAX=F

AW01=6,000  (this could be different depending on the Mississippi withholding form submitted)

When the user tries to input the following (to have additional state income be deducted, which is an option on the state withholding form) a duplicate key error is created:

FT01=A

TARO=25

PTAX=F

AW01=20.00

Is there another way to input this information so the employee can have an additional $20 withheld for SIT for MIssissippi?