That's just how much you want, at a minimum for the item. Your choice, although I would not follow eBay's advice to start at 99 cents to attract bidders.
It doesn't.
The kind of bidder lowball starting prices attract are a pain to deal with.
If you only get one bid, even if it is $100.00, it will sell at 99 cents.
You may also be entering the opening price in the wrong format. Do not use $ and be careful that you are using periods to separate dollars and cents and not commas.