Yes, I guess it can sound confusing. First thing to remember though, is that every single meal does not have to be balanced. Feeding a dog a meal consisting solely of RMBs, or solely fish, or solely offal is a bit like you choosing to have cereal for breakfast, a salad for lunch and a big steak for dinner. He has no more need for every food group to be represented in every single meal than you do. When we talk of percentages in raw dog feeding, it means the
overall diet - not each individual meal. So no need to get caught up in figuring out how much offal each meal requires. It's a lot simpler just to figure that he should get around about 2-3lb of offal over the course of two weeks.
The percentages vary a bit according to exactly what goes into the diet. Generally speaking, you'd be looking at feeding about 70% RMBs. But an RMB needs to be
meaty to qualify as a raw meaty bone

If it's something like chicken necks, wings or frames, well, it's probably not very meaty at all. Conversely, a turkey leg is very meaty. So if you feed the former, you need to add muscle meat to end with an adequate amount of meat. If you feed items such as the turkey leg though, then there's no need to add meat at all. Make some sense? Neither way is "better" than the other, it's just different ways of achieving the same result (i.e. there's nothing wrong with chicken frames, they just need some meat added to make a meal. But if you're lazy like me, then it's easier just to feed the bits that already came with meat attached).
There's no need to be precise, but as a general rule of thumb one would aim for RMBs to have an approximately equal amount of meat to bone. When there's less meat than that, then muscle meat needs to be added (doesn't have to be the same meal) to bring things up to roughly that level. If there's sometimes more meat than that, then it's fine if the next meal has less.
Anyway, I tend to feed meaty parts only (no necks, frames, etc). So my dog gets around 75% of his diet in RMBs. I prefer to err on the high side with offal, so that's about 15% of his diet. And the remaining 10% or so goes to occassional muscle meats, fish, eggs and so forth. That's an approximation - I don't measure, and I generally buy according to what looks good/is available at the relevant time.