With free-choice calcium, chickens are able to regulate their intake to the level that they require. That's probably why many give it free-choice - there's no way to mess it up when the chicken is able to do a better job of adjusting the level themselves.
Totally agree on that point I was just trying to figure out exactly how deficient the mix was (cuz I wanted to know more than anything). Well, that and I wanted to make sure there wasn't too much in it if I used it as a grower or developer mix, etc.
I'll be giving it free choice, certainly. My human brain is a bit too puny to calculate each of their individual needs for calcium