Cisco Unified MeetingPlace, Release 6.x -- About the Optional Modifying Parameter
The modifying parameter, if used, is a value from 0 to 255. For example, Bell Canada uses the modifying parameter as a Service IDentifier (SID). For their Outwats service, the NSF code is not complete unless it has a BFCV of 3 and an SID of 2. Another example is Vari-A-Bill by AT&T which has a BFCV of 9 and an SID of 6.