You have configured a long message in a Default Software Update Plug-in policy, and when the message is displayed on a client computer that is restarting due to patching through Patch Management, the latter portions of the message are not seen, and there are no scroll bars available to scroll down to see it.
Settings > All Settings > Agents/Plug-ins > Software > Patch Management > Windows > [any of the Default or clones of the Default policies] > Restart tab with the Allow restart after installation set to Scheduled or At the end of software update cycle. Notify user about restart is selected, and Use custom notification message is selected.
Patch Management 8.1.x
A fix is available - see INFO5191, CUMULATIVE POST 8.1 RU7 POINT FIXES. This is also fixed in 8.5 RU1