An auto-bump feature that you can buy for 5, 10, 15, however much GB per month.

You can turn it on and off whenever you feel like it.

When enabled, it bumps one of your trades in the trading center every 15 minutes. Probably the trade that hasn't been bumped in the longest. It doesn't matter how many trades you have, it only bumps one every 15 mins, to avoid any kind of spam if you have a ton of trades.