I actually just looked at that page, then came here and saw you posted a link to it. Thanks. So, I'll try that with my game...
cookies = 10.35 - this is all of the cookies, so the cookies are worth just over 500 HC total, which becomes less and less significant as you get more and more HC.
HC = 207.26
Sum of the above: 217.61
Milk = 4.6
kittens are: 1.23, 1.46, 1.92, and 1.92
multiply the kittens and sum of HC/cookies: 217.61*1.23*1.46*1.92*1.92 ~ 1440.59. multiply by 100 to get a percentage, 144,059%
The game says my multiplier is 157,327%. This is close enough that I think I just made a small error... maybe I miscounted my cookies...