The 10% rule is an opinion started years ago. Sorry but ball pythons do NOT do well on large meals. And those who feed large meals with the mythical 10-15% rule will have snakes going off feed to catch up and come posting why are they not eating.
Ive never had a snake go off feed unless was breeding and even then its slim.
But you feed that 10% rule to them and see how well it works. I couldnt imagine someone feeding a 200-300g rat to a ball python.