What do 191 people in Mozambique, 334 in Bahrain and 4,719 in Japan have in common?
They all joined more than one million unique individuals, each of whom who gleaned advice or received inspiration, meaning, community and much more, during this past week at Chabad.org…!
Were he a mathematician, he would have referred to the "more than one million distinct individuals." In mathematics, when you say there is a unique object having a certain property, it means there is only one object with that property. Obviously, there is not a unique person having the property of having visited chabad.org. If you want to assert that n objects have a certain property, and you want to make clear that you didn't count any of those objects twice, you'd say "there are n distinct...."
Consider the statment, "There is one person responsible for cleaning the house for Pesach, the housewife." This statement does not exclude the possibility that the housewife shares the responsibility with someone else. A better way to say it would be "There is a unique person...."
Consider the statement, "There are two people who are responsible for cleaning the house for Pesach: the housewife and the cleaning lady." This statement does not (explicitly) exclude the possibility that the housewife and the cleaning lady are the same person. A better way to say this would be "There are two distinct people...."