The highlights being on the upper rims of the craters is making my mind want to see them as humps rather than depressions. Rotate my Kindle 90 degrees and they become depressions.
Yeah, they do look kind of like “bubbles” rather than depressions in that photo. I think part of it is they seem to be shallower craters than we often see too, either they are older and more weathered, or maybe it is just a trick of the resolution.