What is use of configuring EDIINT AS2ID under external-Id's in trading networks?

Iam New to TN, In webMethods trading network’s external id’s under partner profile, we have option to select differenet types of external id’s …like Dun’s, Mutually Defined, As2 Id etc.

My external system is sending Mutually defined (ZZ) under ISA and GS ( sender qualfier and reciever qualifier )

still do I need to configure EDIINT AS2 ID ? what is the use of external_ id EDIINT AS2 ID? In which case i need to use EDIINT AS2 ID ?

ISA00 00 ZZ4048842166 ZZ9966421432 2301111536U005010001515980T>~

Note:wm.EDIINT:send is used at my end to send response EDI content to external system.

The EDIINT AS2 IDs are passed in the HTTP headers if you specify either primary or secondary HTTP/s as deliveryMethod of wm.EDIINT:send, unless you specify a different external id type.

This is documented in the 8-2-SP1_Module_for_EDIINT_Install_and_Users_Guide.pdf (softwareag.com).