I just got off my summer hours (thank god, way to long of a day) so I am able to get back into the gym in the mornings for cardio.

Currently I'm still trying to cut to get my bf down low as possible before starting my cycle.
I got up this morning, brewed a cup of coffee and went to the gym. I did the treadmill at 15% incline 4mph, tried to keep my heart rate around the 140 mark (my resting is around high 50's-low 60's) for around 30 mins.
After that I went home and ate my eggs than went to work.

Is this the optimal range for fat loss? I also do 20mins cardio after my workouts

I am also keeping my carbs very low for now and my protein high for optimal fat loss currently.

Thanks for any advice brothas!