I need to write this so people understand. help make it understandable without example
When clicking on the thumbnail, sometimes you can see part of the picture that isn't in the frame in the thumbnail. When you click on the thumbnail, the picture pops up showing the whole picture.
The problem is not with the picture that appears when you click on the thumbnail. That's the whole picture. That's the "real" picture.
The problem is with the thumbnail. Because the thumbnail doesn't accurately reflect the entire picture, when you click on it, you see parts you didn't expect to see. Is that a problem? If so, use a cropping tool.