Hey there, your comps are just outside the limits specified by nissan, the only good thing is that they are 150 and above(showing that it hasen
t been thrashed). but seeing how they get lower from 1 to 6 usually indicates that its overheated at some stage and has slighty warped the head (no biggy,just a machine when head gasket gets done). 1 thing i would do also is do a tk head check test. which is a liquid that sits in a bottle that mix's with the fumes from the radiator, this will tell you if the head gasket is on its way out, good for pre purchase inspections.
I dont know everything, this is just things ive been through/seen before.
