So, I have my layers and when I go to
File > Add Slices For Selection to slice the images and then export.
They are coming out with the wrong size, if you take the star, it has a width of 40px on the sheet but when I export it the total width of the image is 60px or so.
Is there a away to make the images export and stay the size I set on the canvas?
I'm not sure how your slices are set up, but have you tried
Trim transparent pixels in the Export panel? If your slice has padding around the actual element you want to export, this should automatically remove it for you.