Question about ammo canisters

[phil74501]

I'm playing a scenario from the 1956 Arab/Israeli war. In the scenario I command British paras. They land with very limited ammo. There are ammo canisters that drop with them. I have to move the paras to the ammo to stock up. I moved all of the squads and mg's next to the canisters. But it appears only one unit at a time loads ammo from them. The ammo load on the other units doesn't increase, even though they're just sitting there doing nothing. My question is, what is the rule on this? Can only one unit at a time draw ammo? How much ammo does a unit load per turn? Thanks