This article gives you an overview of how sub-standards interact with the standard to which they are attached. For information on how to create a sub-standard, please take a look at Add Sub-Standards to a Tracker.
When you add a sub-standard to a standard, the sub-standard will appear in your tracker. To assess the sub-standard, hover over the title of the sub-standard, and click Assess.
The mastery level of the sub-standard is rolled-up to the mastery level. This means that the mastery level of the sub-standard is assigned as the mastery level of the standard.
If you have not assessed the parent standard, mastery levels will not be rolled-up until all sub-standards have been assessed.
After all sub-standards have been assessed for the parent standard, by default, the sub-standard with the lowest mastery level is the one that is rolled-up to the parent.
To change the calculation method of sub-standards, click the Tracker Settings button  to open the Tracker Settings menu and select an option from the Sub-Standard Proficiency menu . You can select to use an "Average" method of calculation for sub-standards instead of using the default lowest score ("Minimum"). Learn more about customizing your tracker settings.
Note: This is only available in trackers where the teachers' respective admins have made Tracker-level settings available.