Putting a ? on a quantifier that isn't variable-length is like having any color car you want, as long as it's black. There's no difference between a greedy and a non-greedy {5}.

A greedy quantifier will take as many characters as it can, and then start backtracking until whatever follows it matches. A non-greedy one will take as few characters as it can, and then take more until whatever is supposed to follow it is found.