Sure. So we are a betting exchange. That means you can choose any odds you like and you will have a bet if someone else agrees to this odds and takes the other side.
The covered odds are odds we you directly will find a match. Someone else is already willing to give you this odds. If you choose the "open" odds, than you will create an open bet and you will need to wait until someone else is willing to bet against you. If no one does the bet will be refunded. So in the beginning we suggest to just take the covered odds, but you should give it a try as well to place an open bet a see if someone else will accept it.
Edit: Thanks magic - that was quick...