so I have PHP code that will create an appointment now, and I need to update it.

I refer to: SourceForge.net Repository - [zimbra] View of /trunk/ZimbraServer/docs/soap-calendar.txt

I find

<ModifyAppointmentRequest id="INVITE_ID_OF_DEFAULT_INVITE" comp="COMPONENT_NUM_DEFAULT_INVITE">
rest is SAME as CreateAppointmentRequest except THE TARGET FOLDER IS IGNORED (see above)
</ModifyAppointmentRequest>

I know the ID from the create response, but what is the COMP? I do not see a COMP returned in the create, nor do I know what this is really?

So is it optional? Or where do I find it?

Thanks!