It should be used in the calculation, but used as a hip roof, not as a non hip roof. When calculating the lineal footage of roof across the entry, only count the width of the raised entry once, do not add additionaly for the house roof across this opening.
I believe your main hang up is in classifying the entry roof type. It is a hip roof, not a gable. A gable roof has a flat face forming a trianglular wall, all you have here are sidewalls underneath a hip roof.
Take the horizontal measurement of the gable roof in the back and devide by the total roof fascia measurement (which includes the front entry lineal footage). If it is less than 10%, the roof is classified as hip. I’m pretty sure you have a hip classification.