Poor calories for walking

Calories depend on your heart rate and time, not directly on the distance or elevation. Also, since there is a 30% difference in time, the Resting Metabolic Rate (RMR) will have a big impact. You better compare the Active Calories of both activities - they will match your expectations better.

Or add 20 minutes of the RMR to the first activity - only then they are comparable. You get the 20 minutes of RMR from your daily Resting Calories (RC) = 20 * RC / (24*60) 

Calories is a measure of energy and mostly depend on weight and distance, not on HR. Yeah, Garmin also uses HR as an approximation, and it requires HR zones to be set correctly, but this is totally ridiculous. My zones are lab tested, and HR for walking is rather low compared to running. RMR calories, for a light-weight woman of a certain age are very low over 20 minutes. That makes close to no difference. The big difference between running and walking is that you use a lot more muscles in running and there's a phase where both feet are off the ground, hence you have to propel yourself into the air. Guess what: I just checked the net calories: they are nearly the same with a difference of 7 between running and walking. Thus something is clearly going wrong here.  Heck, if I walk something like 20km at slow pace, just a relaxed stroll I get about 1500 net calories. That's totally ridiculous. For example this calculator (https://exrx.net/Calculators/WalkRunMETs), which uses METs gives me 600 net calories, and that is fairly realistic, not 1500.

6928399 said:

Calories is a measure of energy and mostly depend on weight and distance, not on HR.

That is true for a simple mechanics, but not for the body. Calories burned by the body can be much better estimated without knowing anything about your pace, distance, elevation, or the weight you carry, just from your body parameters, the Resting Metabolic Rate, the average Resting Heart rate, the real-time HR, and if possible, also the HRV (esp. for the respiratory rate). Some reading is available for example here: Firstbeat Analytics (the provider of the algorithms Garmin uses)

6928399 said:

RMR calories, for a light-weight woman of a certain age are very low over 20 minutes.

It would be around 20 Calories.

If you think the Calories during walks are too high, check you heart rate graph. More details here: Burned Calories Calculated on My Garmin Device Are Wrong | Garmin Customer Support

If you find the Calories expenditure during your walks and runs does not correspond to the heart rate graphs, please contact the Support, and report the issue to them.

Looks like your pace was much faster on the first one, so your average heart rate was probably higher.

Dude, the first is running and the second walking.

Doesn't matter. You are still moving your body weight a certain distance from point A to point B at a certain pace/speed, and at a certain heart rate. Based on that... those calorie burns look fine to me. Not sure what you are expecting.