"They" must be smokin somthin. I've installed cams in a few different engines and almost always the stock settings are recommended. The clearance between the heel or flat side is not going to change regardless of the lift height or aggressiveness of the cams profile. Set them to stock specs, .005/.006 cold. The specs for that cam would be helpful, but they're not really necessary for setting valve lash. Unless that cam has some kind of HUGE lift, or it's made from some crap steel that expands like a hot dog cooking on a grill, in which case it wouldn't even idle and couldn't be practical for a rig driven on the street or trail, I say ignore those guys, but heah, that's just my opinion.
One more thing, is the spec they told you in inches or milimeters? either way it's freakin big.