Rower vs Outdoor Walk Calories

Hi folks,

I recently got a rowing machine and don’t believe the watch is calculating calories correctly, has anyone else seen the same issue? Example from today below:

I went on an outdoor walk today, 30 minutes, average BPM 98, watch shows 174 (active) calories burned, or 10.35 calories per minute.

in comparison, I did a 20 minute rowing workout, average BPM 143, watch shows 144 (active) calories burned, or 8.33 per minute.

There are more examples like this. I’m always sweaty after the rower but hardly ever after a walk, which workout is getting over/under calculated?

Also for comparison, I connect my rower to a polar heart rate monitor, and today’s rower workout showed 477 calories burned. I glance at BPM both on the watch and the rower during the workout and they are within 1-2 beats of each other.