Apologies. I'm always very scatter brained, and also sleep deprived if you must know, heh.
I meant to write that it is being powered by the barrel jack with a 9 volt, not usb. I don't have the gauge connected so no voltage divider, just my bench power supply.
I just measured 5 volt pin and everything is accurate, btw this is one of those chinese knockoff arduino boards, I have some genuinos that I will use for the real thing, this is just a test arduino for code prototypes