Reading HR cam question - HELP!

I am trying to "read" my new cam

Cam is a 287/298 duration with .512/.525 lift

Reading the lift at the lobe, I am getting .308 and .313 between intake exhaust and intake.

Simple math tells me
.308 x 1.6 = .492
.313 x 1.6 = .500

I read the cam installed in the block, off the lifter and off the lobe itself using a dial indicator on a magnetic base zeroed on the base circle of each lobe.

Am I reading the cam incorrectly, is my math wrong or is the cam ground wrong?