How GL account is derived on discount line of an Invoice

hi,

Mr. Binapani ask us to post here.

here the background:

we setup the gl account number to receivables transaction based on the header transaction type.

now if that transaction invoice including a discount or a promo line, the gl account number for that discount/promo line (if we click the distribution button) it shows different account number from what we setup in transaction type.

so our question is where can we setup/change that gl number for that type of line in receivable transaction.

thanks beforehand if anyone would like to respond.