FRMLS_SPEC_USAGE is a standard SAP Structure so does not store data like a database table does. It can be used to define the fields of other actual tables or to process "RM22: Value Assignment Type - Usage Assignment" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately. i.e. DATA: wa_FRMLS_SPEC_USAGE TYPE FRMLS_SPEC_USAGE.
The FRMLS_SPEC_USAGE table consists of various fields, each holding specific information or linking keys about RM22: Value Assignment Type - Usage Assignment data available in SAP. These include SUBID (Substance), ESTCAT (Value Assignment Type), VACLID (Rating), RVLID (Validity Area)... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .