Dont understand natural number+ symbol. what does it mean

Question

I know and understand what natural numbers are, but what does it mean when the natural number symbol has a + at the top, in the position the squared number would be. Can't seem to find information anywhere about it. 

 

in the question: find set and cardinality of {n ∈ naturalNumber+ : n < 1} what is it really asking for? and could someone guide me through the problem. Thanks 

Answer 1

I don't know what N⁺ is, either.  I am doubtful that it's a kind of qualification (meaning only positive natural numbers), because that's inappropriate, violating the definition that excludes negatives and zero integers).

 

Then I see that n<1 is part of this inquiry.  So I believe that the answer is the EMPTY SET, Ø