This is something that we need to document as it may cause user confusion.
The values displayed in the enterprise console UI for message count trend upward over time, irregardless of the data collection interval.
For example, at 12:00 the user starts the JON server+agent, deploys an ESB archive and before 13:00 sends 1000 messages through the a service deployed in the ESB archive.
If the user later specifies a data "Metric Collection Schedule" of from 14:00 to 15:00, this being a time period when no messages are being processed by the service, the message count metric displayed will still be 1000.
The only way that the user can get the message counter to display a zero value is to reset the counter.