If you click on the market bottom it will show you the current price the two are trading at, how much you have available. I tend to stick to leave the current price as is if I feel I'm getting a good deal, you can game it all you want, but transactions/swaps happen quicker when you don't try to get more for less. After it is STEEM the drop down will give you an option to power it up.
I see, it use to just have a convert in the drop down instead of the market view. Thanks!