Day selections in time group include 00 (confusing)

The Month Day Start and Month Day Finish options in a time group default to "00." This is confusing, since there is no day 0 on a calendar, and there is also a single dash available as a menu selection here.

If a user wants the whole month to be part of the time group, should they be selecting the 00s or the dashes? Not sure of the difference between - and 00. Do they have to select Day 1 through Day 31, or can they just leave it as dash or 00?

There could be some more tooltips or instructions on this page helping a user know how to make a selection.

Note: the month selection menus default to dashes and don't contain any 00 entries. Suggested improvement would be for the day menus to match this default and for there to be no 00s. Would like to see some more instructions on this page.