The stick-on thermometer is measuring the glass temperature, which will fall somewhere between wort and air temp. The bigger question is whether or not it's even accurate. You should stick a lab thermometer inside the wort and calibrate it (so to speak) yourself.
The article in BYOB this month seemed questionable ... author said the wort temp in the middle will be higher than nearer the edges. That seems very suspicious, especially in an actively churning fermentation. No data supported that claim.
No one gives a doggy doo, about your stupid home brew.