What's the callback field for in the to do list?

[Pamoola]

I can add "callback" field from the contack field chooser list in the
"to-do-list" in calendar. But in the column under the field name, what can
be put in there? I cannot find any help in Microsoft.

 

[Diane Poremsky [MVP]]

it's the phone number for calling someone back. While it can be added to
tasks, it can't hold data on tasks, only contacts.