If you look at the screenshot, application assignment is just below the assessment, and assessment says criminality in progress which makes me think that the due date is for criminality.
Also, it was assigned to RC-9515 which I think is the agent code for RCMP officer. They seem to have a code for each office and officers. Office code (shown as RC code in notes) has only numbers whereas agent code starts with first one or two letters of office name followed by a number (in this case, RCMP agent code is RC-9515 and CPC agent code is CP03900). Some more examples
Office Codes:
RC Code - 6262
Office Name - Centralized Intake Office
RC Code- 9245
Office Name - Operations Support Centre
RC Code -9518
Office Name -CPC Vegreville
Agent Codes:
If it's updated by an automated system to reassign/distribute files between office, it shows something like
Updated By: SADMIN, CONV_ADMIN etc. (this may be the user id of automated system used to run distribution jobs)
If it's updated by an agent (human), then it shows something like
Updated By: C8296 or CP03900 etc. (this may be an agent code who manually updated)
Reference for support:
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/bulletins-2012/376-january-19-2012.html
Disclaimer: This is completely based on my understanding. And my understanding is my understanding, none of your understanding.