To give you a quick answer …
The value of the rackback is between 9-11% which we just say is ~10%. What that is based on is the level of table you play at. For example if you’re playing at a $.25/$.50 table, you’d be at 9%. If you’re at a higher end table, you’ll be at the 11%. It is basically linear in between, i.e. play a mid-range table and you’re probably around 10%.
Does that sufficiently answer your questions?