Note: All pages below are subject to having relevant Roles and Permissions.
From the left Menu go Config > Curriculum > Configurations.

The Configuration area sets the Timetable Defaults used to define the amount of time that will be allocated to Classes and Registration Periods.

Simply enter the duration (in minutes) for AM Reg Duration and PM Reg Duration.
The Class Duration field allows you to set a default duration for all classes (excluding AM and PM Registration).
The Max Class Duration is the maximum amount of time for any Class that takes place.