Active hours identify the period of time when you expect the device to be in use. Automatic restarts after an update will occur outside of the active hours.
By default, active hours are from 8 AM to 5 PM. Users can change the active hours manually with a max active hours range of 18 hours by default.
Starting with Windows 10 version 1703, administrators can specify the max active hours range users can set. This option gives you additional flexibility to leave some of the decision for active hours on the user’s side, while making sure you allow enough time for updating. The specified range will be counted from the active hours start time.
This tutorial will show you how to specify the maximum number of hours from the start time that users can set their active hours for Windows Update auto-restarts in Windows 10.