Thanks for the replies, dude.

The reason why I'm asking is that I'm learning a song for a band. On the chord chart it says Fm13. I'm not sure what exactly is meant by that.

Does it mean F-m13 or Fm-13? In the first case, what you said would hold true, that intervals in the upper octave are rarely labled with a minor or major. If such is the case, then the chord would be an Fb13. If the second is true, the chord would be a minor 7th with a 6th.

I don't understand why you're adding all the other crap - the 9th and 11th. Aren't 13ths just a dom7th and a maj6th?