Optimizing on Zeropark

Hi guys, i might start a follow along on my campaigns on zeropark this week. But before that i have a question about optimizing on zeropark.

Here are the stats of one of my campaigns :

So i spent 542$ and made back 234$ with an ROI of -56.89% and 117 conversions.
As you can see from my second screenshot i have a few good targets but then most of them have only 1 ...