Why did my Export Files double in number???

Gents,
  Last night I had to export 6 tracks of vocals for a project. 3 tracks of lead vox, 3 tracks of chorus harmonies.
  I recorded them all normally, and ***converted to mono*** (if this is important in this discussion).
    The guy wanted them back as broadcast wav files, so just to be safe, I carefully went over all the steps for that in the "HELP" section. So I do everything, and in the little box on bottom left, I have the tracks I wanted to export highlighted. They were:
    Track 4 leadvox1
    Track 5 leadvox2
    Track 6 leadvox 3
    Track 7 chorus1
    Track 8 chorus2
    Track 9 chorus3
 
So everything's cool, settings are how he wanted it , and I export them. However, once it's done, I now have ELEVEN files, not 6.  For example Track 4 leadvox1-1, Track 4 leadvox1-2, Track7 chorus1-1,Track 7 chorus 1-2, etc.  I forget which file didn't get doubled, I'm on a different computer right now.
 
Ok, NOW it's 2am, and I have NO CLUE which tracks are the ones I actually want to send to the guy...I'm 6 hours into this and exhausted, and really don't want to hear this tune ever again in my life, so I'm not about to listen to them all...so i just sent all of them...I'll spare you the story of sending 11 tracks at 2:30 in the morning that take 6 minutes each to upload and then half of them time out mid upload F*CK!
 
Anyway, the guy calls me this morning and says they sound great, and he thinks I actually SANG on 11 different tracks. He's super happy he has so much stuff to choose from!
 
So things worked out I guess, but my question is WHY DID THE NUMBER OF TRACKS DOUBLE??? I would definitely want to avoid this in the future, so any suggestions will be deeply appreciated!
 
TIA,
Michael Lee

I converted to mono before export. You may be right about the dual mono thing, but he said all tracks have vocals on them? When recording, there are two lines inside the track, one showing the vocal patterns and one just a straight line, so if it went dual mono, wouldn't one track just be devoid of sound?
 
Thanks!

Did you export "clips"? Maybe they're discreet edits/files.