No problem. I also found this on Blue Coat's support site. You'll probably need to log in to read it.
According to the article, for concurrent connections, the MIB you will want is 1.3.6.1.4.1.3417.2.11.3.1.3.1.
Also, the attached PDF from Blue Coat provides all the appropriate MIB numbers for monitoring critical resources on your Blue Coat ProxySG. Please note that wherever the document has a MIB number starting with "SNMPv2-SMI::enterprises", replace that with "1.3.6.1.4.1".