Yes,
The unit will recall just the number and position of ammo quantity that match with the original OOB.
What is very interesting is the inverse situation:
Begin a scenario with units with the same weapon's configuration, but with very low ammo levels (quantity of 2-4).
Then bring on as reinforcements, ammo carriers and... there you have an interesting situation.
Your depleted (from ammo modified units) will stock up to the original ammo levels as soon as they come close with an ammo provider unit.
This is great for situations like for example the ammo resupplying of airborn Para units by the use of airdroped ammo containers etc...
IMO, this might be a good reason, why the modified units should (after all) recall the original OOB ammo levels.
cheers,
Pyros