Well wait for someone with more experience to back me up here, but if it were me I'd set it in such a way that the glass is the temperature that you want.. because most of them will burrow straight down to the glass anyways..
In my opinion you don't want the temperature of the glass to get hotter than you'd be comfortable with your BP laying on it, because it's likely that it'll be laying straight on the tank anyways. Just my 2 cents.
Like I said, wait for someone else to back me up![]()