N/A.
The behaviour is currently by design.
The 'Hotword Hits' column is a part of the Hotword Analysis feature and displays an aggregate count of hotwords identified in the email item based on the Searches selected in the Search Facet. Hit Highlight navigation considers all the selected Searches and the combined respective hotwords used in those Searches which caused the email item to be considered as a hit. Additionally, it would consider those Searches which did not go through Hotword Analysis processing as well. It is therefore possible the sum of the count of hotwords found in an item (top level message and attachments) from Hit Highlight navigation can differ from the 'Hotword Hits' column count.
Note - Hit Highlight Navigation also works without Hotword Analysis.
In Veritas Advanced Supervision Web Client: