This report is especially useful for Engage Messaging or Facebook Messenger channels because on those channels, one thread generally corresponds to one inquiry. To allow this data to be as accurate as possible, agents should remember to close a thread when a conversation is over on Engage Messaging or Facebook Messenger.
The ‘Messages by …’ reports are not really suitable for these channels because the interest is on the number of open discussion threads rather than on the number of messages sent / received.
For example, suppose that in the current period 15 discussion threads were created on Engage Messaging (Tellme Mobile Android) and 72 on Engage Chat. Those numbers represent the number of contacts respectively for the channels.