Special GL indicator F is not defined for down payments

Hello All

In F-47, throws message u201CSpecial GL indicator F is not defined for down payments". If I use GL Indicator A instead of F, I got a screen wherein No feilds for entering PO number or PO Item number

Please let me know

(i) whether shall I use indicator A instead of F

(ii) if so how to enter PO related info in the screen

Advance Thanks for sharing your inputs

Regards

Thiru