I find the calculator on the Mexico site to be rather inaccurate for me, but everyone varies. Age and surgery type, as well as co-morbidities all impact weight loss rate. It thinks I should be at 212lbs at 6 months but I'm at 240 with 6 days to go. Not gonna happen. It also thinks I should be at 170 by 12 months, but that's not very likely either.
I've always used the following one as it takes into account the different surgeries and looks just like the one my surgeon uses. They calculate from the highest weight, it is important to include that because if you have a lot of weight loss before surgery your percentages may track differently and your post op weight loss may be slower. I've seen this happen to several people with surgeons calculating it improperly, or applying the bypass trajectory to a DS patient, which is a disaster and very stressful for the patient! This one takes into account much more like your age, ethnicity, and pre-existing conditions:
https://riskcalculator.facs.org/bariatric/?_ga=2.112690692.1282950073.1698781773-393992475.1698781773
According to this one I should be at 78 lbs down for my DS surgery at 6 months. I'm at 80 lbs down. My weight loss has tracked along with this thing pretty steadily, give or take 15 lbs, since surgery, except for my 6 week stall. It puts me at 202 by 12 months out, but DS patients lose for 18-24 months post op, so I should be at 170 sometime in that 12-24 month period!
In the end these are all just estimation tools. Our bodies do what they will and we make the most of it. Still, it is nice to have a loose guideline to follow.