Q: Why does my "Estimated profit" shows a negative number?
A: Estimated profit is negative for all items because estimated profit is essentially your compare item price (which is the selling price scraped from your compare item URLs) - supplier price - approximate fees. Since you're not entering compare item URLs, then compare price is 0 and anything subtracted from 0 would be a negative number. This does not mean that you're not making a profit. You just haven't entered compare item URLs, which are optional.
Here's a video on compare item URLs for eBay sellers - https://www.youtube.com/watch?v=si2Vuezf2q0
Also here's a video on estimated profit - https://www.youtube.com/watch?v=NnHQtDs-LMc
Please note that we don't recommend compare item URLs for eBay sellers -- it will result in lowering your sell-thru ratio - it's mentioned in the video for compare item URLs for eBay sellers. But if you choose to add them, that video will also show you how.