Overestimating calories burned and weight loss

I have several questions for folks with HRM

1) when you log your calories burned, do you log what your HRM shows for that time (gross), or do you subtract your BMR before logging (net)? My Polar FT60 with chest strap takes into account my age, gender, weight, average HR, highest HR, VO2 max, etc. When I do 60' of cardio kickfit with weighted gloves & ankle weights, my HRM gives me ~265 calories, So minus the 55 calories I would burn in 60' without exercise = 210 exercise calories (3.5 calories/minutes) even though I am sweating profusely & breathing heavily at the end.

I had been inputting gross but I think I need to go back and recalculate them all to input only net calories burned.

2) do you know what calculation/formula your HRM uses to give calories burned? I have never found a calculator that gives as low a gross burn as my Polar calculates. When I use this formula
Female: ((-59.3954 + (0.45 x HR) + (0.380 x VO2max) + (0.103 x W) + (0.274 x A))/4.184) x 60 x T a session with T(ime) 28minutes 54 seconds, average HR 121bpm, VO2max 33, W(eight) 115#, age 50, it shows 184 gross calories yet my HRM shows 124 gross calories for that session. That is 2 calories per minute difference!!

My Fitbit and other trackers estimate much higher, but they don't know HR or VO2max so I don't trust them.

thx for any insight