Hours per day
Supported on: At least Windows Server 2008 R2 or Windows 7
Registry
HKCU
software\policies\microsoft\office\16.0\ms project\options\calendar Options
default hours/day text Description
Defines the number of hours that you want Project to assign to a task when the user enters a duration of one day. If you enable this setting, day-long tasks will be assigned the number of hours that you specified. If you disable or do not configure this setting, the user's default setting is used.