It also seems to make clear that the type of potassium salt you are taking (chloride, citrate, gluconate, acetate, bicarbonate, etc) does not matter. The only thing that counts is the amount of actual (elemental) potassium you are ingesting.
Legal custody of a child means having the right and the obligation to make decisions about a child's upbringing. A parent with legal custody can make decisions about the child's schooling, religious upbringing and medical care, for example. In many states, courts regularly award joint legal custody, which means that the decision making is shared by both parents.
There is a difference between physical custody which designates where the child will actually live and legal custody which gives the custodial parent(s) the right to make decisions for the child's welfare. If the parents agree, the court can award joint custody, physical and/or legal.