WotLK Question about buying gold

[Secyto31]

What does "Duration" mean? Should i mind that before buying gold?

[Persivaln]

After enabling 2FA you have to wait 3 full day (72 hours) before you'll be able to use Trade section. And iirc, there is some downtime period for coins that were gifted, for same sake of security.
Upd. Just got what you were asking exactly. Duration is time period during which your trade offer will be up on site for other players (and during which you won't have any access to whatever item you've put on Trade). It appears only on "Sale" page for you, so you probably should switch it to "Buy" in case you want to but gold using Warmane coins