Urgency
- https://www.debian.org/doc/manuals/developers-reference/pkgs.html
- https://www.debian.org/doc/debian-policy/#s-f-urgency
- https://www.debian.org/devel/testing
- https://lists.debian.org/debian-mentors/2008/02/msg00567.html
IIRC valid options are:
lowmediumhighemergency(I think)critical(I think)
A default of low is sensible.