Hi Coyote,
You are correct: there was one set of defintiions released on the 4th.
Details on each of September's Multiple Daily Definition releases for SEP can be found here:
http://www.symantec.com/business/security_response/definitions/multipledaily/detail.jsp?mdid=2011-09
That included the definitions version, new detection added, etc. Each of the certified releases made in a day are listed there.
Generally 2-3 certfifed definition sets are rleased each day, but on occassion there will be only one.
Hope this helps!
Thanks and best regards,
Mick