View the dwarf's inventory, then select the quiver and press Enter to view its contents.
That's what I've been doing, but the game tricked me. It never showed any bolts and I assumed the interface just didn't show bolts that way. If what you say is true (and I believe that it is) then my quivers have always been empty when I looked, which is an aha moment for me. My guess is that they probably don't fill their quivers at all until receiving their first combat posting or deciding for the first time to practice. Possibly, they may even empty their quivers when going inactive (although I doubt that). I will expermient a little more today to figure out their behavior in more detail.
In version 0.31.xx, dwarves perform archery practice using ammunition stored in their quivers. Note that this also means that a dwarf whose quiver is completely filled with combat-only ammo will never practice.
Thank's for that, it's good to know. It implies that they don't ever empty quivers, only fill them. BTW, is there any information on how many bolts/arrows a quiver will hold? I don't remember seeing that anywhere.
Oh, and now that you have me thinking of these things, another question that's been bugging me (and why I was trying to count bolts in the first place), what does it mean to specify X number of bolts for a squad on the ammunition tab? Say I have a squad with 5 axedwarfs and 5 marksdwarfs and I specify 100 metal bolts for combat on the ammunition screen? I assume that each marksdwarf will take 20 bolts from the stockpile, but for all I know the first couple that get there might take 50 and leave the others will none. Or does that screen mean that each of the marksdwarfs will try to take 100 bolts?
I'll be experimenting with these a little myself this afternoon, but thank you for your help.