Patches › jobs lists every round. Open one that is still waiting, then press cancel. The second press is what stops it.
The list under the form is every job, newest first. September security round is scheduled: it installs everything already approved, on Reception PC, inside an eight hour window, and restarts only if an update needs it. It is waiting for its time. Click the name for the report.
The report names the machine, the window, and who scheduled it. While the status is scheduled, the line under the title says it is waiting for its time. cancel is the red button on that title. A job that has already finished shows close instead.
Press cancel. The label turns into a confirm. Press it again to stop the job. This shot stops on the confirm, so September security round is still scheduled. The same confirm applies to a job that is already running: machines that have not started are skipped, and one that is already installing finishes on its own.
Scheduling the round is Schedule a patch install. What each machine still needs is See which machines a patch is for.