ZCM 11.2.3a agent update applied to all devices.

I have upgraded our development server from zcm 11.2 to zcm 11.2.3a and manually selected to update the agent on one workstation.
This all went well.

Now I see the update is set for all devices.
When I install the original ZCM 11.2 agent on a machine it installs fine and then after a reboot the agent auto uipdates itself to to ZCM 11.2.3a

We have 7000 devices and I need to stagger the agent update in the production environment.
How do you think this was set to all devices and can I change it back to select specific devices and stages for delployment.

Under system update the only available option is to delete the update.
Should I delete it and then import it again and one downloaded completely try and deploy to individual machine ??

Thanks
Mark