"Ammunition X" means that you didn't need to reload... as you get X Ammunitions
In facts, each tim you shoot, you use an Ammunition, so you check one box.
Valombre gets one order that can boost his gun
by using more ammunitions ; using this order spend
more ammunition CMD for one shoot, but your shoot is clearly more powerfull !
Welcome in Hell
[EDIT] Sorry ! The Valombre's order didn't cost any more ammunition