The time and date formats follow the strftime format. A simple google search for 'strftime' or a 'man 3 strftime' on Unix should be able to help you there.
Warning is the text to display if a text item contains a %w and the protocol for the notification does not support warning levels. This would be any protocols besides AIM or ICQ.
Ellipsis is the text to use when clipping text. If your clipping format for text items is set to truncate this option has no effect.