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The default calendar view is the Month view. All your leads within that month will appear on the scheduled callback day, in the order of the time of day the callback is scheduled for. Click a callback from the Calendar. You will be redirected to the Feed page for that specific lead. Once you have made a disposition, you will be redirected back to the Calendar page.
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Callers view is limited to their own callbacks. Any private callback for the Caller will appear in Green as shown below in the screenshot.
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Managers view is limited to their own callbacks and any user who is assigned under the manager. Managers will see their own callbacks in Green and their assigned agents callbacks in Blue as shown below in the screenshot.:
Calendar View - Owner
Owners view displays all the callback of all the users in their organization, even without any assignment.