size of /var/db/freebsd-update

Hi,

I recently upgraded a vm from 12.2-p7 to 13.0-p4 with freebsd-update.

% sudo du -sh /var/db/freebsd-update/
1.5G  /var/db/freebsd-update/

I thought it's a relatively large chunk of space to have just for that.

Then had a look at a system that had been in existence since 2017-10-11
when it ran 12.0-current as it was then (r324534) that had by 2019-09-09
been upgraded to 12.0-RELEASE-p10 (r352201) and was from then on updated
with freebsd-update, at intervals, all the way from 12.1-RELEASE-p1 through
to 12.2-RELEASE-p7 and from there to 13.0-RELEASE-p3 and now to 
13.0-RELEASE-p4

$ sudo du -sh /var/db/freebsd-update
5.8G  /var/db/freebsd-update

this is a huge amount of space, as the vm is 64GB. What can I do to free 
up the space without breaking freebsd-update? I guess it's the update history
but couldn't find anything in the manpage on how to maintain it
with regards to size.

thanks,
-- 
J.