Outer Limits 4x4 Board

I was watching an OBC video that had some in car footage of Chris Hummer's car and noticed that his oil pressure gauge rose and fell with engine revs.
I start mine and the gauge goes to 95% and only drops when engine oil is low or revs are below 700rpm,
but then only down to 80%.
Is my gauge reading correctly.
Cheers

my gauge is an aftermarket job which reads in PSI,at idle it sits at 20+-
and up around 5000rpm it reads 80+-.