Can I update my IMac operating system - I have a late 2013 IMac and this page say OK in one place and not OK in another.

I have a IMac late 2013 27 inch and would like to update the operating system. The sight from apple that shows how to do this has two different contradicting specification requirements to do this. One says I can update the late 2013 model while the other doesn’t list this model. Which is right?