As Ger21 stated there is nothing wrong at all with the toolpaths that Sheetcam has generated. It is moving your bit along a nice continuos path in order to keep the cutter moving at as constant a speed as possible. This helps to avoid having the feed of your machine start and stop at every corner. Remember that when you look at the toolpaths they represent the center point of your round cutter, not the geometry of your finished part. This is something I got used to after awhile, but it can be a bit confusing at first. If you are working with some cheap material the best thing I can suggest is to simply let your machine cut out the part ans watch it carefully as it moves. I think that watching your machine move around following the paths that Sheetcam has generated is the best way to learn and understand what is actually going on. Good luck to you, I have had excellent results with Sheetcam!