That is one of the more annoying errors.
1. If you use the same image on multiple props... such as matrices, mega-trees, and smaller props. To get rid of the error, you have to shrink the size to the smallest prop, and live with terrible quality images on your larger props, or copy the images multiple times, change the larger, medium, and smaller file name accordingly.
2. Especially on videos, if you reduce the format and size it can greatly reduce the quality of the images.
I cleaned up all my sequences once and was able to remove all the errors, but did not notice in the preview video how much quality difference there was. Uploaded everything to production and family came home asking why all the images looked so bad. Went outside and the display looked terrible. I had to restore from backup. Before you get carried away cleaning up the file sizes, make sure you backup beforehand, and then go out and look at the quality after.
I don't think you can disable the file size error separately, but it is a feature I would disable if it was ever offered. I don't think it is a bad error to have as an option, but it would be nice to have the option to turn that one off, so it is not mixed in with the errors you want to see.