Aggregators gather altmetric data from a variety of sources. They vary in what they collect and how they present the data. For a helpful comparison and suggestions on interpreting the data presented, see:
Chamberlain, S. (2013). Consuming Article-Level Metrics: Observations and Lessons. Information Standards Quarterly, v. 25, no. 2, 4-13. doi: 10.3789/isqv25no2.2013.02
Note: MU does not currently have a full subscription to Plum Analytics (Plum X) so there is no access to the research impact dashboard.