abap/aab_log_field_size_limit is a SAP Parameter attribute which is used to control maximum log size for individual fields in ASSERT-Log (in Bytes) 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 .
If using addition FIELDS for ABAP statement ASSERT, all values of the
specified fields are stored in the assertion log (if the operation mode
is set to log, and the ASSERT statement has been violated). The
parameter specifies a maximum size for each field. If this exceeded, the
value is truncated.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.