You never want any part of the snake's home to be over 90* and since your snake is ground-dwelling (not flying around in the middle of the cage ) I'd suggest you go by the "floor" temp.

Most likely your thermometer is not accurate- many such things are very poor quality, especially those round-stick-on types sold cheaply by pet stores. If that's what you're using, I'd suggest you invest in an accurate temp. gun & throw those away.

When you talking about the difference between keeping a snake healthy or endangering their life with a 5 degree difference, you really have to make sure, don't you think? Excess heat can cause permanent neurological damage in snakes, or result in serious & painful burns or their death. And the heat can really build up in an enclosed cage from a 100 watt bulb- which is why it (and ALL heating devices) should be connected to a thermostat for safety. Obviously it's not, & that is a recipe for disaster.