I'm overweight and walk about an hour to an hour and a half every day. Having worn a CGM for a week I was able to see that exercise has very little, sometimes no, effect on my levels. Even though I'm walking at a decent pace and raising my heart rate. Having spoken to a dietician who is also T1 diabetic, she tells me that if it's an activity you do regularly over a long period of time your body adjusts to that being the norm.
Running, when I used to be able for it, used to raise my levels of I ran over about 5 miles thanks to my liver kicking in.
So, the point I'm trying to make its that you can't really use the calorie to carb ratio to work it out as the liver and other factors effecting glucose levels can't be reckoned for.