Inaccurate Calories

I know that there must be dozens of similar post regarding this. I have searched far and wide.

But I just couldn't get this fixed.

I have a Garmin Fenix 8 bought last week.

I am 37yo. 5'6 and 195lbs.

My profile is in metrics and I have correctly input my weight and height.

In general, I have a Resting calories of 2141 in a day according to Garmin Connect.

Here are my HR and Zones:

maxHR = 183bpm

LTHR = 166bpm

Resting HR = 58 bpm

Based on BPM

Z5 = >152 bpm

Z4 = 136-152 bpm

Z3 = 119-135 bpm

Z2 = 102-118 bpm

Z1 = 85-101 bpm

On Feb 28, I burned a total of 3185 Active calories on top of my Resting calories.

I did inclined treadmill walking for 1hour, 4.38km and lost 911 calories. 155 avg bpm. Machine tells me I lost around 400 calories.

I did strength training for 23mins and lost 259 calories. 129 ave bpm

I went to the mall for the rest of the day. App gives me a total of 12km distance with 16k steps this day.

Minimum heart rate is 54bpm and max 169 bpm

3185 active calories + 2141 resting calories for a total of 5326 seems unbelievable..

On March 1, I burned a total of 1550 Active calories on top of my Resting calories. A total of 3691 calories

I almost did nothing this day. Except my regular daily activity of cooking, watching tv, a little bit of work in my seat for a couple of hours.

The app told me I took 5559 steps.

Minimum 56bpm and max 135bpm

On March 3, I burned 2122 Active calories on top of my Resting calories. A total of 4263 calories

I did inclined treadmill walking for 10mins. 0.73km and lost 147 calories. 149 ave bpm..

I did Muay Thai and kept my watch under the gloves. 3 mins per round and 1 min rest in between. With 5 rounds. Activity time is 29mins. Burned 374 calories. 146 ave bpm.

Minimum 57bpm and max 177 bpm perhaps during Muay Thai.

App gives me a total of 5.9km distance with 7285 steps this day.

I have mentioned that I have search far and wide. I did setup my profile correctly. I setup my maxHR (not sure if correctly.) And setup my zones (not sure if correct).

So I changed my maxHR to 170BPM. Reset the zones to default which is the same as the above mentioned zones..

Today, March 5, 7:12pm GMT+8  as of this writing. I burned 2201 Active calories and 1680 Resting. (Note that it is still not the end off the day.)

I did strength training for 37min and lost 448 calories. 125 ave bpm

I did Muay Thai and kept my watch under the gloves. 3 mins per round and 1 min rest in between. With 5 round. Activity time is  30mins. Lost 469 calories. Ave 156 bpm

Min 57 bpm and Max 183 bpm during muay thai

Already burned 3802 of Active and Resting calories .

This is my first Garmin watch. A smart watch that cost more than 1kUSD. Coming from a cheap Xiaomi and Samsung watch. They give me similar results and almost the same with treadmill machine.

While this expensive thing gives me almost 100% of over estimation. Hence this very long post.

What am I doing wrong here?