When I list ammo on the flea market, the numbers sold and the numbers listed don't match up. I am not running any mods, just a straight install of B5.
I listed 300 rounds (5 stacks of 60) of 5.45x39mm BS rounds for 1800/round. The in game flea market shows my listing as 60 rounds of BS ammo, but my profile shows my offer as 5 individual stacks of 60 rounds of BS ammo (totaling 300 rounds).
After checking my plain-text profile, I tried logging back in to check on the status of the offer and I get the 443 "missing key" error that many people have reported in the last week. When I go back to my plain-text profile, it now shows 2 stacks of 60 rounds of BS ammo remaining. After several cycles of trying to log on then checking the plain text profile, my offer FINALLY trickle sells and I am able to log in.
(As an aside, the "443/key missing" bug seems to be directly related to a pending flea market offer. If you have offers pending, you may see the bug. When your offers sell, the bug will resolve itself. Deleting all of your active offers in your profile seems to alleviate this bug as well.)
When I log back in, my Ragman message log shows 10 sales where a total of 64 BS rounds are sold. First 3, then 1, then 8 sales totaling 60 rounds. I have tested this with 180 BS rounds, 300 BS rounds, and 750 7n31 rounds. Every time I list multiple stacks, all but one of the stacks is sold as if it were a single round, then the last stack trickle sells so that the total number of rounds sold is stack size+(stacks listed-1). 180 BS rounds turns into 62, 300 BS rounds turns into 64, 750 7n31 rounds turns into 64 rounds.
This has happened every time i have tried to list ammunition on the flea.
This does not appear to happen with non-stack-able items. I listed 5x 30-round val magazines for 50k each. Flea market shows a listing for 1x 30-round val magazine listed at 50k even though 5 magazines were listed. The magazines sell over a few transactions (4 magazines in first one, 1 magazine in second one) and Ragman gives me 250k. I have sold batches of 10-15 barter items, meds, and mods/magazines and they have all sold fine in my experience, so I think it is the items with a stack size that are selling incorrectly.