The current auction durations in the sell tab say 12, 24, and 48 hours but the correct times are actually 2, 8, and 24 hours as seen in the regular auctions tab

The classic version of auctionator is unofficial, but you can find the fix you are looking for here:
https://www.wowinterface.com/downloads/info24958-AuctionatorClassicquickfix.html

Closing, this is dependant on #402 - and resolving that will resolve this.