I can't really see how this is going. Did you copy & pasted?
If the first set, {1 2 3 4 ... 57 58} is A = {1~58}, n{A} = 58.
The bottom one, {3, 4, 5, 6, 59, 60}.. I think you meant {3~60?} let's just call that B, because we can't have 2 As.
n(B) = 58.
ok. They both have 58