Sabund and Rabund files

I have a question about certain files’ characteristics: I think I cannot fully grasp the difference between Sabund and Rabund files. For example, talking about the the Sabund file, the manual says that the second column represents the # of OTU categories that have been formed (http://www.mothur.org/wiki/Sabund_file). About the Rabund file, the manual says that the second column represents the # of OTUs that have been formed (http://www.mothur.org/wiki/Rabund_file). This description is really confusing to me. I get even more confused when I look at the description the manual does about the following columns in these two files. Could you help me to clarify?
Thanks
Letizia

Letizia,

Yes, this is one of the more confusing things in mothur. The second column of the sabund file indicates the number of sequences in the dominant OTU. So if the number is 5 then there is at least one OTU with 5 sequences in it, but there aren’t any larger. I’ve altered the text slightly in the wiki. Let me know if you still find this confusing.

Pat