What does Avg. promoted per collection/category in Dashboard mean?

Avg. promoted per collection means the average number of 'Pinned Products' which are active in the set of collections or categories synced with Tagalys. 

e.g. you have 2 collections synced with Tagalys. Collection A has '0' products pinned whereas Collection B has '10' products pinned. The Avg. Promoted per collection is '5'.