The Identified Prospects Comparison viewport shows you how many prospects were identified month over month, compared to the previous fiscal year.
This viewport tracks each time a prospect was identified, based on when they moved into that stage (including if they were created in an identified stage). It is not a measure of the prospects currently in an identified stage.
The data from the year selected is compared to data from the previous year (if available). Your system admin is responsible for mapping your institution's prospect stages to "identified" as appropriate. (They also can map stages to other values not displayed in this viewport.)