I can comment on that. I grew up in metric system, and that was a standard formula for calculating normal weight, only for women it was your Height minus 110; and for a ballerina/young lady it was your height minus 115

So, my height is 169 cm (5'6 and 1/2") My normal weight with 110 formula was 60 kg which translates into something like 133 lbs, and the calculators here in Imperial normally peg my 'ideal' weight at 130-135 lbs range as well based on what size frame you put in (the formula of the 5 for every inch over 5 feet will peg me at 130-133 lbs as well if you count my half inch, LOL!).

But I was always more comfortable with 54-56 lbs range (which is your 120-125 lbs), which is consistent with the '-115' rule, and the lower end of the healthy BMI spectrum (the cut-off is somewhere between 114 -118 lbs for my height in Imperial).

My HOT STUFF! weight will be more around 50 -52 kg (110-115 lbs) providing I preserve muscular mass, obviously!

Uhm, what I am trying to say, those numbers correspond well enough, and one probably needs to adjust them in front of the mirror