Is my substrate warm enough

Hi all. Sorry for the beginner question but does my substrate need to be 91 degrees or just the actual bottom of my tank? Because my thermometer, which has a sensor right above the heat pad, is reading 91 degrees but when i put my hand on the substrate there seems to be no difference in temperature between the hot and cold side. I am using Repti-bark if that helps. Thanks for all the help!

Just the bottom of the tank. The substrate shouldn't be too deep though.

For you're "doesn't feel different" thought, our hands aren't very good thermometers in this temperature range. The best way to find out would be a non-contact (infrared) thermometer.

So I got a temperature gun today and it seems that on the hot side that the temperature of the substrate is mostly staying around the mid 80s but my thermometer is at 93 degrees. Should I leave it how it is or increase the temperature?

Do not increase the temp. Just the action of your Ball slithering around to get into a ball will cause substrate to move out from the bottom of the tank.