Setup Polar HRM for more accurate calorie burn for known BMR

According to these steps I should input my age as 58 and weight at 55lbs?? Explain to me how this is going to give me a correct reading on the calories I am burning? *lol* My brain does not like math...

Well, if you have suppressed your metabolism by underfeeding it (netting below your BMR constantly), then you don't really burn as much as you think, nor as much as the Polar estimates.
A slower metabolism means everything you do expends less energy than it could burn.
The Polar knows that at this HR for this age person with this max HR, burns so many more calories than they would at BMR level. Well, if yours is lower, best to inform the HRM.

So for the HRM to have a better estimate of what your slower metabolism is doing, you are adjusting the stats so it is more correct.

So I'm assuming you correctly went for the second set of instructions since you may eat or net at 1200 or less?

Now, if you start following a lot of the advice topics starting up about eating more to lose more faster, than you should re-adjust at that time.

I usually net 900-1000, but I EAT 1400 to 1500 calories, and just don't eat back my exercise calories. I have lost 130 lbs with no plateaus doing this, have a ton of energy etc, so I am reluctant to change anything at this point. I am also on the short side at a smidgen over 5´ Of course maybe my HRM is over stating what I burn and there fore I am eating more, who knows. *lol*

So your BMR is probably below 1200 actually, so you are hitting.

And your HRM overestimating your burn, if that has caused you to eat more, has probably kept you from lowering it at all or that bad.

That's why you could adjust for a week and see that probably, you aren't creating that small of a NET, probably closer to 1100-1200, in which case, depending on your body comp BMR, you may actually be using the upper steps for correction.

Soo...
I'm 24. My BMR was 1389, bf% of 18.3 which puts me to 1405 and my new age to 20.
Then for my new weight instead of 129 it should be 85lbs to make my net 1200?

Is this to make your burns less if you are trying to lose slower, or make them more accurate.
So complicated!

This has nothing to do with how much you burn. But to know better what you really are.
This is if you eat back exercise calories and want it to be more accurate.
If you have suppressed your BMR, you are already burning less no matter what the HRM says. In fact eating more would probably help in that regard, but some want to lose slower, so thought I'd support that effort.

So you are combining the 2 methods which is not right.
If you really do eat or NET at 1350, then only use the second one. Because the estimated BMR figure is meaningless, because you made your own BMR figure at 1350.

But that is interesting, you could have a BMR of 1405 if it was fed enough. Mighty close..

So, if you really do eat at 1350 and normally eat back your exercise calories, your BMR estimate of 1405 could be right on.
You are in one of those gray areas. Accidentally protecting yourself.

I would actually put your age to 20, and rest of the stats correct.

And really be good about eating back those exercise calories, because you are burning more than you knew! And you want to keep it that way.