Trade bug?

(sorry if this has already been addressed - I did try to search for it)

I had a little issue in a current trade - my trade partner thought he asked for 4 of something from me, but now that we have sent our cards, he noticed that only 2 were included (on the trading screen). 

I believe him (and I'm sure we can resolve the trade in a friendly fashion), but only 2 were available in my tradelist, so here's my question:  does the quantity automatically reduce to the amount available when a trade is proposed or accepted?  I.e., perhaps 4 were entered, but it dropped down to the 2 I had available as soon as the trade was finalized?

If so, is there a warning that occurs?

Thanks for looking into this.  As always, thanks for the amazing site!
-Tom