Where can I find more about sysstat in the Internet?

I already got the meanings of sysstat & 0xF, but the bit pattern definitions seem unreacheable.

(Although one shouldn't rely on system tables for user scripts, Microsoft recommended script for calling stored procs uses them: http://support.microsoft.com/default...b;en-us;320916)

I'm also very curious to understand how sysstat & 0xF can produce even numbers.