Altmetric, currently available in CityU Scholars, is a system that tracks the attention that research outputs such as scholarly articles and datasets receive online... . It pulls data from different sources such as social media like Twitter, Facebook, and Google+, traditional media of both mainstream (The Guardian, New York Times) and field specific (New Scientist, Bird Watching), blogs and online reference managers like Mendeley and CiteULike. In CityU Scholars, Altmetric will be displayed in the research output record and the search result/browsing list if available. If you would like to explore more about Altmetric, you may go to the webpage: What is Altmetric and what does it provide? to have a look. Read more
The Altmetric Attention Score for a research output provides an indicator of the amount of attention that it has received. The score is a weighted count and derived from an automated algorithm.... It represents a weighted count of the amount of attention we've picked up for a research output. Note that only the FIRST mention from a source counts towards the score. You may have more details regarding the calculation and default weightings from this webpage: How is the Altmetric Attention Score calculated? Read more
*The image was captured on 18 Jan 2019.
The Altmetric details page for the specific research output can be reached in CityU Scholars by clicking the badge on the right of the research output title in search result/browse list, or by clicking the button 
in the research output record if available.
Here is a video by Altmetric introducing the Altmetric details page in around 3 minutes' time.
You may have further information in this webpage: Introduction to the Altmetric details page