Values for GMCODE field can ben found into table T158G.
┌────────┬───────┬──────────────────────────────────────────────────────────┐
│ GMCODE │ TCODE │ Description │
├────────┼───────┼──────────────────────────────────────────────────────────┤
│ 1 │ MB01 │ GM_Code 01: Goods receipt for purchase order │
│ 2 │ MB31 │ GM_Code 02: Goods receipt for production order │
│ 3 │ MB1A │ GM_Code 03: Goods issue │
│ 4 │ MB1B │ GM_Code 04: Transfer posting │
│ 5 │ MB1C │ GM_Code 05: Other goods receipts │
│ 6 │ MB11 │ GM_Code 06: Reversal of goods movements │
│ 7 │ MB04 │ GM_Code 07: Subsequent adjustment to a subcontract order │
└────────┴───────┴──────────────────────────────────────────────────────────┘