I have Citracal petites (because that's what I could find when I bought them). Each serving contains 400mg of calcium, 12.5 mcg (500 IU) of vitamin D3, 5 mg of sodium. Each serving is 2 caplets, so 200 mg per caplet. So 3 needed for 600 mg, 4 needed for 800 mg. I've used them and found them helpful, but just one caplet isn't enough.
Being a person with a million allergies and sensitivities, I spend a large portion of time reading labels. Even of things I've bought before. I find things changed all the time on labels, you can never be sure you are getting the same thing as before, unless you check every, single, time.
I have even contacted companies on occasion, because they change formulations and don't indicate anything on the main label, and you wouldn't know if you don't read the entire label and ingredients. 99.9 % of the time, they don't care. User beware. I even bought a product I'd been using for years, removed it from the box and tossed the box. Had a reaction, nothing was on the container of the actual product, all information was on the box. Had to dig it out of the trash to check. Contacted the company to no avail. They changed formula "based on supply chain issues". You can never assume anything any more. 
Being a person with a million allergies and sensitivities, I spend a large portion of time reading labels. Even of things I've bought before. I find things changed all the time on labels, you can never be sure you are getting the same thing as before, unless you check every, single, time.

