If I looked right then the Extreme is a single cam, right? Single cams usually don't have even tiller measurements as normally taken because the cam and idler are of different sizes and/or orientation. There are two recommended ways to tiller a single cam and both are correct. One is to bottom out the limbs and back them off evenly till reaching desired weight. The other is to stretch a string from one axle to the other and measure to the string from the limb pockets.

And you also may have just found out why a lot of us on these boards do almost all our own work. Because we get it right and can blame noone if it is WR------G. What's that word Arthur?