I see that Maretron’s DSM150 and DSM250 displays have a DCM100 configuration setting called "Instance:"; what is this?

Maretron's DSM150 and DSM250 displays have a DCM100 configuration setting called "Instance:", which is used to program the DCM100 to transmit the appropriate NMEA 2000 instance. For example, if the DCM100 is connected to a DC source, then this configuration setting would be used to program the DCM100 to transmit instance 0, allowing the user to determine which DC source is viewed.