Raffael Stocker <r.stocker@mnet-mail.de> writes:

in the Org Agenda clockcheck view, a warning about missing end time of a
clocked-in task is displayed together with the already elapsed time of
that task.  If the starting time is in the future (this can happen if
rounding and continuous clocking are used), the elapsed time is
incorrect.  For example, if a clocked-in task starts in 5 minutes,
clockcheck will report something like "No end time: (0:55)".  It would
be more sensible to say "No end time: (-0:05)" or even "No end time: (in
0:05)".

Thanks for reporting!
Fixed, on main.
https://git.savannah.gnu.org/cgit/emacs/org-mode.git/commit/?id=ee58259bc

 The culprit is the use of ‘org-duration-from-minutes’ in
 ‘org-agenda-show-clocking-issues’, because org-duration always assumes
 positive durations and is given a negative one here.  The problem can
 easily be corrected with something like the following:
...
 However, I believe it would be more useful (and general) to use a
 similar trick to teach org-duration to work with negative durations.

That's what I ended up doing.

... It would be more sensible to ... or even "No end time: (in 0:05)".

I find this confusing, so I left -0:05.