The verb 'are' has been omitted--perhaps to save space on the sign.
Ex: All specials are good Monday through Friday.
Grammar, not *grammer.
(not a professional teacher) I just wanted to draw attention to the other important alteration Soup made. You'll notice that Soup changed "Mondays" to "Monday" and "Fridays" to "Friday". If you want the sign to read naturally for native English speakers, note that distinction.