Question about SK hand rankings

[GrekeHaus]

Most of you are familiar with these, you can see them at:

http://www.decf.berkeley.edu/~chubukov/rankings.html

My understanding was that these rankings assume that you're only going to get called when you're behind, and your opponent will fold every other time.

However, when I ran the numbers, I got different answers. I set up the equation like so:

SP=stealing percentage
WP=win percentage when called
X=size of your stack

Then we get

EV(push) = 1.5SP + (1-SP)*[(X+1.5)*WP + (1-WP)(-X)]

To figure out what X needs to be to break even, set the EV=0 and solve for X giving:

X = [1.5SP/(SP-1) - 1.5WP]/(2WP-1)

For KK then, we get SP=1218/1225 and WP=0.2262. Plugging these numbers in gave me a value of around 477, which differs significantly from the ones posted at the web site.

What's up with this?