Are you guys talking about carbing with sugar? Because if so, that temp in the calculator is highest temp the beer reached since it was completely finished fermentation. Right? So, if a beer finished at 68f but then warmed up to 80f, but you cooled it to 30f... ypu still use 80f in the calculator. That temp calculation is trying to account for residual CO2, and 80f would be when it off gassed the most. If the beer is done fermenting, chilling it back to 30f wont suck back in CO2.