This COBOL system treats any COMP data items in your RM/COBOL source program as the standard Micro Focus COBOL DISPLAY format. The difference in the internal representation of such data in the two systems is that this COBOL system always sets the most significant four bits of each byte to the value 3, while the RM/COBOL system always sets such bits to the value 0.
For example, under the RM/COBOL system:
PIC 999 COMP VALUE 123
is held in three bytes as hexadecimal value 01 02 03
while under this COBOL system:
PIC 999 VALUE 123
is held in three bytes as hexadecimal value 31 32 33.