For some really weird reason ammunition use and tracking has generated a lot of attention and subsystems over the years. I suspect part of it is from folks coming over from skirmish level wargaming... i.e. Warhammer where ammo tracking is based on dice rolls because tracking the precise ammo use of 10-100 different guys would be a pain in the butt. Others claim keeping track of individual arrows flies in the face of the abstract nature of D&D combat which is nonsense an arrow in your opponent isn't abstract, there is nothing abstract in the discrete capacity to harm a foe 100-600 feet away at one chance per arrow. It's gotta be a new thing because I don't recall bumping into the issue in the 20th century.
Here how I track ammo when there is no spaces for it on a character or equipment sheets:
I I I I I I I I I I I I I I I I I I I I
I cross one off as a I shoot, If I can reclaim it or get a new arrow I put another little line at the end. It works every time, no fiddly rules to worry about.
Why get more complicated?