To specify what items you want the weaponbox to contain, you must turn Smart Edit mode off and add attributes. Enter the item's name as the KEY, and how many of that item you want to give as the VALUE. For example, a key of "weapon_handgrenade" with a value of "2" will add to the canister 10 grenades (as each weapon_handgrenade gives 5 grenades). These are all the valid item names:

1: item_battery

2: item_healthkit

3: weapon_glock

4: ammo_glock

5: weapon_mp5

6: ammo_mp5

7: ammo_mp5grenades

8: weapon_shotgun

9: ammo_shotgun

10: weapon_crossbow

11: ammo_crossbow

12: weapon_revolver

13: ammo_revolver

14: weapon_rpg

15: ammo_rpg

16: ammo_uranium

17: weapon_handgrenade

18: weapon_tripmine

19: weapon_satchel

20: weapon_snark

21: weapon_hivehand

22: weapon_crowbar

23: weapon_gauss

24: weapon_egon

25: item_longjump

26: item_suit

Chance of appearing (chance)

From 1-100, this is the chance that this entity has to spawn on the level.