You use SAP enhancement MBCFC004 EXIT_SAPMM07M_004, which contains function module exit EXIT_SAPMM07M_004 to classify user-defined characteristics automatically during goods movements in Inventory Management.
This is only possible for characteristics which are not assigned values during quality inspection.
As opposed to modifications, enhancements are release-insensitive as they are not made in the SAP standard version but in name ranges reserved for the customer.
For more information on the general procedure for making enhancements, see enhancement transaction under menu path "Utilities - online manual".
Each individual enhancement is documented. You can find this documentation if you choose "SAP Docu" in the enhancement transaction.