The number of arguments in the activating element must be equal to the number of formal parameters in the activated element,
with the exception of trailing formal parameters that are specified with an OPTIONAL phrase in the PROCEDURE DIVISION header of the activated element and are omitted from the list of arguments of the activating element.
If the numbers of operands are different, then if there are more operands in the activating statement, they are ignored and if there are more operands in the PROCEDURE DIVISION header, they must not be referenced within the activated runtime element. The positional correspondence may vary depending on the non-COBOL calling conventions implied by mnemonic-name. Any mismatch in the number of the operands will only be apparent at run time and so the directive FLAG does not cause this extension to be flagged.
The rules for conformance between arguments and formal parameters depend on whether either the formal parameter or its corresponding argument is a group item or both are elementary items.