A negative percent increase is the same as percent decrease. For example, in aerobic cellular respiration 686 kcal in one mole of glucose in transferred into 304 kcal in 38 moles of ATP. If you plug 686 and 304 into the above calculator boxes and click on solve, the result is 55.68513119533528% which rounds off to 56 percent. In other words, the energy decrease (dissipated) is 56 percent and the efficiency is 44 percent.
$80 reduced to $40 is a decrease of 50%, but $40 raised to $80 is an increase of 100%

