The one we have is an infrared thermometer and I have two inside the tank that give temp and humidity.
So the infrared one might be part of the issue. The digital ones you have inside the tank, if they don't have probes, are only measuring air temperature. You need to be measuring surface temperature. Surface temperature is what is being referred to when you read advice on recommended temperatures.
Typically, an IR thermometer would be giving you surface temperatures, however, IR guns are reliant on the surface they are measuring being within their calibration range. If the surface material is not within the IR guns calibrated materials, the reading will be off.
Without getting technical, every material has a specific E-Value. Most IR guns come factory set to measure surface temps of items around .95 E-Value. Any material with a higher or lower E-Value will provide false readings. While .95 E-Value covers many common materials, it also is very far off of some common materials which might be found within a bearded dragons enclosure.
For that reason, I recommend digital thermometers with probes over IR guns. If using an IR gun, you need to be accuracy checking it with a digital with probe end first to verify your IR gun is measuring your specific materials surface temperature properly. Of course, once you've verified the temperature's agree between your IR gun and your digital with probe end, you don't need to keep checking with your probes since you know your IR gun is measuring that specific material properly. You do need to do this check with the different materials you want to measure in your enclosure though.
TLDR, your basking surface temp may/may not be a much different temperature than you think it is if you are using your IR gun to measure the surface temp without verifying it with a digital WITH PROBE END.