Try this:
[PRODUCT:100:30:AMMO:ITEM_AMMO_SLINGSTONES:GET_MATERIAL_FROM_REAGENT:A:NONE]
Alright, I changed my raws to this and now something very perculiar is happening:
I created a new world, embarked and dug some stone. Buld a craftshop and ordered the making of
1 cloth sling
1 cloth quiver
1 slingstones (which should yield 30 stones)
now what happened:
a clothier brought cloth and made 10(!) slings!
a clothier brought no cloth and didn't make a quiver, job was still 'done'
a stonecrafter brought no boulder to the shop, didn't make any slingstones and made 0 slingstones, the job was still 'done'
I have no idea how this could be happening.
[REACTION:MAKE_SLINGSTONES]
[NAME:make slingstones (from stone)]
[BUILDING:CRAFTSMAN:CUSTOM_SHIFT_B]
[REAGENT:A:BOULDER:NO_SUBTYPE:NONE:NONE][WORTHLESS_STONE_ONLY]
[PRODUCT:100:30:AMMO:ITEM_AMMO_SLINGSTONES:GET_MATERIAL_FROM_REAGENT:A:NONE]
[SKILL:STONECRAFT]
[REACTION:MAKE_SLING_LEATHER]
[NAME:make sling (from leather)]
[BUILDING:CRAFTSMAN:CUSTOM_SHIFT_L]
[REAGENT:A:1:SKIN_TANNED:NONE:NONE:NONE]
[PRODUCT:100:1:WEAPON:ITEM_WEAPON_SLING:GET_MATERIAL_FROM_REAGENT:A:NONE]
[SKILL:LEATHERWORK]
[REACTION:MAKE_SLING_CLOTH]
[NAME:make sling (from cloth)]
[BUILDING:CRAFTSMAN:CUSTOM_SHIFT_S]
[REAGENT:A:1:CLOTH:NONE:NONE:NONE]
[PRODUCT:100:1:WEAPON:ITEM_WEAPON_SLING:GET_MATERIAL_FROM_REAGENT:A:NONE]
[SKILL:WEAVING]
[REACTION:WEAVE_CLOTH_QUIVER]
[NAME:weave cloth quiver]
[BUILDING:CRAFTSMAN:NONE]
[REAGENT:A:1:CLOTH:NONE:NONE:NONE][DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[PRODUCT:100:1:QUIVER:NONE:GET_MATERIAL_FROM_REAGENT:A:NONE]
[SKILL:CLOTHESMAKING]