Why don't the values for Duration appear as drop-down list values?

Duration is not a drop-down list (picklist) attribute. It is a select control attribute, and allows users to type in any value. Because the select control is not part of the Microsoft Dynamics CRM Online database schema, it can't be changed in the same way you would set the default for a drop-down list (picklist) attribute.

To change the default value for a select control, you can use an OnLoad event for the form. For example, the following code would change the default duration on the Appointment form to 5 minutes.

if (crmForm.FormType == 1)

{

crmForm.all.scheduleddurationminutes.DataValue = 5;

}