By default, CMD and eContact use a barcode identifier built from from three numbers, unique to each event participant:
- Record number of the event
- The unique Participant ID for the Contact in that event
- The Contact’s record number
That center number, the participant ID, can change as guests are added or removed from your event. This information can be useful at a moment in time, but is ignored at check-in by eContact, eContact offline check-in, and CMD.