As Adam says.
I've got a screw in comp gauge that has short braided steel line and uses air fitting to clip onto spark plug fitting. It always reads about 20 lb lower than push in style comp gauges. I've had the gauge calibration checked and was fine. I figure it's the extra few CC's in the fitting and line lowers it.
Also reading will change, depending on how fast your starter is cranking it.
What you have looks OK.