The Influencer Score is intended to be a gauge of the reach of a Teams user's messages. It is calculated as the number of members sent to multiplied by the number of messages sent. For example, a Teams user who sent 8 messages to a total of 65 people would have an Influencer Score of 520.
There is no "good" score for the Influencer Score as it will depend greatly on the number of users in your organization. However, it is helpful to see Influencer Scores relative to other users.