Pipelining was really kicking off in a big way and suddenly IPC made as big a difference at a time amd led in that regard as clock speed so amd started numbering their cpu models with a number that was based on the MHz they'd expect an Intel CPU to need to reach to match it.

Of course intel also released new CPUs and AMD didn't want their newer CPUs to have lower numbers than their old one, so that number eventually got inflated.