Consumables and ammo works the same.
If you use x-grog only once, you'll use the whole item at the end of the mission.
If you use 2 separate instances of the "x-grog" item, their individual charges will be summed up to refill as many complete items as possible.
Same is true for ammo. All bullets will be counted and filled up to form a complete item of ammo.
Huh... I was under the distinct impression that the amount of ammo/charges is tallied then however much is left over (compared to max amount) is the % chance that the item will be saved. So if it has 20 shots and you only use 4 then there's an 80% chance that it will still be around when the mission ends.
Ive gone through missions using some kinda expensive/rare ammo and after firing a few rounds from it the clip will still be saved. I mean those UAC plasma rifle batteries are rare until you can make them, having just a couple its pretty relieving to take the weapon into battle and use it, and come back without having expended a clip.
Maybe the RNG just hates me at the moment and has chewed through like 7 X-Grogs simply for using a few charges from them.
Edit - Another interesting dilemma ive been having is Stunned Enemies not being captured. I had a humanist pogrom the other day where I knocked out the leader with a knuckleduster and he wasn't bleeding out. However by the end of the mission he just died anyway. WTF is going on with that, if they're stunned and they arent bleeding out then why are the dying.
I can understand if they're technically alive on the last round and they have bleeding then that bleeding might be applied one more time and they die at the end of the last round. But if they arent bleeding then they shouldnt be losing health (and in fact their stun should be decreasing).
I also just had a sky ninja mission and there were 4 sky ninjas, one of them was bleeding x6 at the end when I killed the last other ninja. But at the end of the mission it listed that I had only killed
and recovered 3 ninjas. So something in the game goofed up about that one that was wounded because there were 4 ninjas and none of them were overkilled (shotguns and flintlocks here).