The GOT field is filled in when you collect the weapon, and the PREF field is used to indicate which weapon slot should be used for a specific weapon, and the PREF slots can be filled in by using the SETUP.INI file with the field "slotX" where X is a number between 1 and 9 and the field value should be the name (with folder) of the gun you want defaulting at that slot. You can also set this pref field using the new LUA command SetWeaponSlot ( weaponindex, got value, pref value ).
PC SPECS: Windows 8.1 Pro 64-bit, Intel Core i7-5930K (PASSMARK:13645), NVIDIA Geforce GTX 980 GPU (PASSMARK:9762) , 32GB RAM