subsquent debit

HEllo

What is the meaning of subsquent debit and subsquent credit?

in my scenario for one PO with quantity 12 and priice is 9 Dollar/without matreial(only short text) this PO base invoice verification.

i have seen here in PO histotry one 93 Doollar for IR document generated and SUB debit for 4 Dollar.

for one line item two documents possible in SAP?