good call on this, but removing the % sign leaves no space anymore and the number looks funky all the way over like that. I heard the percent sign was actually an image. Would you happen to know where to get to it, so I can just fill it with a blank image?
Those % images are packaged into a .artwork file. You would have to extract that artwork file which contains about 1,800 images, thumb through them, replace the % images, repackage all images as an artwork file, and then add the artwork file back to your phone. Not an easy task, but not impossible either.
If you're a Winterboard user you should be able to theme it. The images are named: