you're going to have to monitor the thermostat and floor temperatures for at least a day to figure out what to set the thermostat to. with my T8, i have my Herpstat set to (i think) 98° F to achieve a 90° hotspot. for the glass enclosure, the Herpstat is set to (again, i think) 95° to achieve a 90° hotspot.
everyone's environment is different, so how my thermostats are set might not work for you. you're just going to have to monitor the setup until you have everything dialed in.