Gauge Temp Lower Than Radiator Temp..??

Just for everyone's information. I wanted to mention this is an "Aftermarket" mechanical gauge I have installed. It is a sunpro gauge from advanced auto. I thought I mentioned it before in my original posting. No biggy.....LOL I just did not want everyone to think this is an electrical gauge. Just a a plain ole mechanical one.
I figured I would just remove it this weekend and toss the probe end in some water on the stove and bring it up to a specified temp and compare it to the meat thermometer and compere apples to apples.
NOTE; the gauge in the original cluster "Does " appear to be working. How accurate it is is another story. I'm not for sure what each mark represents on the cluster gauge.