Contacts can be set as the default number. What does this setting do? How to cancel?

The default number can be considered the preferred number. After setting, the default number will be displayed when you quickly search for contacts in the phone book or dialer, and when adding contacts directly when sending a new text message. The default number cannot be canceled directly (compared to Motorola's Milestone 2, which does not have this function), but it can be changed by long pressing another number in the contact and setting that number as the default number.