Thanks Mutt,
So you mean, since engines can produce a larger amount of thrust in colder temperatures (obviously over the flat-rated temperature), a larger percentage is taken off as penalty for the Power Management Computer being inoperative, ( as the computer has more power to manage in colder temperature conditions which produce more thrust , without which we would manually not be able to extract peak thrust performance from the engines.)
Mav...
p.s: any more explanations are requested / welcome