30 degrees from what?

So, everywhere I look people are saying “getting an ear is easy! Just score it all the way across with a 30 degree angle. It’s so easy!” But what does 30 degrees mean‽ 30 degrees from what? 30 degrees from the table it’s sitting on? Is it the angle of the blade as it enters the dough, or it is 30 degrees up the surface of the dough? Or something I’m not thinking of? Any help would be awesome. Thanks!