All this math makes my head hurt lol!
I've yet to make my first batch of soap (SOON, but for now, reading, reading, reading) so my words hold no weight, but this is what SoapCalc says in the FAQ section
"2. Can I use SoapCalc for making goats milk soap?
Yes, just put the milk (or milk/water solution) where you would put the water in SoapCalc. If you are not familiar with making soap with milk SoapCalc strongly suggests reading about it here: Making Milk based Soap at About.com (or getting a good book about it). When making soap with milk products as the liquid, some procedures are different from making soap with water as the liquid. Also check out the links at the bottom left of the above referenced web page."
I took that to mean it should be counted as water only. Procedures are different (in order to avoid scorching, etc) but formulation should be for water.
Again...maybe I'm having a brain fart, but that's how I read it.