This seems like an odd statement...

If the outside temperature is 97F, and the temp limit is 77F, this would be a 20F reduction in air temperature. If the outside temperature is lower (say 80F), then it would take much less energy to drop the temperature by 10F. It seems like if there is a limit to the amount of energy that can be used in ECO mode, they should specify that the system can REDUCE the temperature by a certain amount.

77F seems like an arbitrary number to me...