No, (but YOU GOT IT RIGHT, just may of got tangled in my wordy words) if my tank reaches .3°C above 25°C (you have to have a tolerance) the fan will come on then stay on trying to bring it back to 25°C which is the target. ...and happens to be 77°f. If my tank drops to .3°C below 25°C (again you have to have a tolerance) my heater will come on and attempt to bring it back to the 25°C.
........................All this C and f stuff is because the STC-1000 only talks C.... and my brain likes f.......
This gives the differential temperature in the tank +/- .54° f. or +/- .3° C, for a total of 1.08°f or .6°C.
However, I did make a mistake in my math. If both the fan and the heater do succeed in bringing the temp back to target the tank will vary from 77.54° and 76.46°f. I had stated the low side at 76.44°f.
In fact, I had to calibrate the STC-1000 and my tank had dropped to 24.4°C because the STC was off by .4°C (the STC-1000 thought it was at 24.8°C) so after I recalibrated, the heater did come on and brought the tank back to the target in about 25 minutes.
What is cool is that my tank which was over heated this time of day, today actually was .6°C below the target, because of the fan doing its job... even well enough to go below the target... .... and the STC-1000 actually did bring it right back onto target.
OK.. I'm hooked!!!