Why net discount base is amount included tax in t-code F-53 but not in FBZ2

Question

dear all expert SAP consultant
i am here need your help..i have case where the discount amount in F-53 is different with FBZ2. but all the configuration and amount in the both transaction are the same even the currency. for the detail here is scenario. hope you can help me solve this problem.
i set the configuration for discount base amount is net procedure. where it means that the discount amount is taken from invoice amount not included tax. e.g. invoice amount 909, tax amount 10% =91, and total to be paid before tax is 1000. if the discount is 10%, therefore its amount should be 91 too. but when i run the transaction (f-53) the discount is 10 not 91.so the base amount for discount 10 is 1000(total to be paid where is included tax) not 909( not included tax).
just a note : this configuration takes a right effect if you do the transaction in fbz2(outgoing payment with PO). why this configuration doesn't take effect in transaction outgoing payment without PO (f-53).
i really hope your help.
anyone who can help me is so appreciated.
warm regard
land lord

Answer 1

thank a lot chandra..but the discount is still taken from amount included tax. eventhough i have set discount base amount is net procedure. where the discount amount should be taken from amount exclude tax.
but thank you for your help...
warm regard,
land lord