What is Credit memo and subsequent debit in Logistics Invoice verification?

The term credit memo refers to the credit memo from the vendor.
Therefore posting a credit memo always leads to a debit posting on the
vendor account. Credit memos are used if the quantity invoiced is higher
than the quantity received or if part of the quantity was returned.

Accounting entries are : Vendor account is debited and GR/IR account is
credited.

Subsequent debit : If a transaction has already been invoiced and
additional costs are invoiced later, then subsequent debit is necessary. In
this case you can debit the material with additional costs, i.e. GR/IR
account debit and Vendor account credit. When entering the Subsequent
debit, if there is no sufficient stock coverage, only the portion for the
available stock gets posted to the stock account and rest is posted to the
price difference account.