stat/as_bufsize is a SAP Parameter attribute which is used to control Application staticstics: SHM buffer size information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
The records closed in the application statistics are stored temporarilly
in a buffer in the shared memory. Parameter stat/as_bufsize specifies
the size of this buffer (in bytes).
See SAP Parameter Documentation for full SAP documentation for this profile parameter.