I have the same thermometer.
The thermometer is made for in house use, with the probe running outside. So the "in" temperature is the temperature of the area around the thermometer display, the "out" temperature is the temperature at the the probe.
The reason the "out" temperature on your thermometer is lower than the set temperature on the thermostat is because the heat has to go through the plastic container. So in order to reach 90 degrees or so at the thermometer probe, you'll probably have to set your thermostat to 99 degrees or so (at least mine does). Experiment with it and see.
Your "in" temperature is the ambient temp in your enclosure. If that is reading 68 degrees, it is WAY too low. You need to get it to more like 78 degrees to keep your snake healthy. A UTH won't affect the ambient temperature much, you need another heat source. Either use a lamp or ceramic heater, or just get the temperature in the room the snake is housed in higher.
Your "out" temperature is a little low, but it's probably ok.
What is your humidity?
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