System Mapping issue when trying to update step number

I am attempting to correct an issue where live attendees were accidentally added as Attended On-Demand.

When I try to save, I get the error "Attended must come before Attended On-demand".

We have our event campaigns synced to SFDC. Could this be why there is a System Mapping area in the Channel setup which is not referenced in any of the Marketo documentation?

How can I correct this and get my live attendees to the proper "Attended" status?