So on my treadmill, speed is in mph - example 2.3 mph. So I’m not sure if you’re saying the same thing.
And elevation is adjustable in .5 increments. This isn’t identified as degrees, so I’m not sure how to compare.
After a heart attack 8 years ago, I set it at 2.3 mph -2.6 mph for 30 minutes and adjust elevation to keep my heart in the target range.
Consistency seems to be the key
2.3 miles in 60 minutes for you compares with my 1 mile in 23-24 minutes = 2.5 miles per hour.
The treadmill has 0.5 degree adjustments. I start out with 4 clicks which is 2 degrees. After 15 minutes I drop it to 1.5 degrees. As soon as the treadmill shows I have covered one mile, I stop.
Then I workout with the weight machine for 10 minutes, pulling light weights with 1 break.