It looks like the icon for the app reserves some space under the PNG used for the main icon for additional images it uses to cue you to other issues. Take a look at this screenshot which shows one example on the Ambiant-MATE theme with the Familiar panel:
When I initially loaded the app, I initially saw just some diagonal lines under the icon without the red background you see in the screenshot above. I think that's what @wolfman thought was text. If you use Caja to search your file system for the keyword "boinc" you'll find the actual icons used, and may be able to find the additional images in the program folder to help understand what those images are.
There may be an issue with the Boinc icons used in some panels being too large for the available space as described in a previous post associated with some other apps. I'm not sure if that's involved here or not.