It's not 22.4 rating to 1% parry. It's 23.65 rating to 1%.
Now some bright person will point to the blue post going zomg22.4. I invite you to grab a calculator and do some math while unequipping and equipping a piece of gear with parry rating while in game.
(You can get all the significant digits you want by multiplying the base parry rating of 15 by (level + 12)/52, or 15x82/52 = 23.65384616 for level 70 - see Combat rating system - WoWWiki, which is correct)
Ya a number of guides and sites including my own had mistakenly used the 22.4 number. For some time now my site has been updated with the correct 23.65 value for 1% parry. I try my best to notify any website owners that use the incorrect values.