Your offer will remain up either till the amount of sats are drained or until someone outbids you for the top 5 spot, if that persons offer expires you will move back into the top 5. If you click the donate button, you'll see righ at the bottom, how much you need to donate (amount of total sats/days you want it up) to remain in the top 5

I think yours was set for 1.85 sats per day, while the lowest for top 5 is 2.72 sats per day.

I've used it several times and I rather shorten the period so I remain in the top 3 for less sats