Canvas allows you to customise the updates and notifications - and the frequency of these - that you receive for your courses. When you update your notification preferences you are updating them to apply to all of your modules.
You can choose to set your notification preferences to notify right immediately, get a daily summary, a weekly summary, or turn off notifications completely.
More Information
You can find a full list of the Canvas notification settings at the following link:
Canvas Notification Settings (PDF)