I noticed this too. Unless most of the 57,812 firearms are stashed away in evidence or testing/id collections, the FBI has a serious ammo shortage. Even if a 10th of the firearms are active-duty, they have an ammo shortage.
For me a normal day at the range will consume between 100 and 200 rounds, about five times as many as they have in storage per weapon. At that it looks like their agents may not be getting anywhere as much range time as they need.