Field help (PIHLINACC1) 

These fields indicate the purchase accounting accounts. The charts of accounts that can be accessed depend on the account core model associated with the company of the movement. If these fields are not entered the account will be automatically determined by the accounting code for the product according to the setups for the automatic journal.
SEEINFO The presence of this field depends on the entry transaction used.
These accounts are loaded by default according to the accounts displayed on the document line from which the invoice line is originated.
SEEWARNING When no product code is displayed on the line the main account must be entered.