Apostrophe

A new restaurant has opened in St Andrews on College Street. I think it does Indian and fish food. Not “fish food”, like food that you give to fish, I mean seafood. You know what I mean …
I just hope that their food is better than their grasp of punctuation, as the sign outside reads:
OPEN-7 DAY’S
What’s with the apostrophe?! “Days” is plural not possessive!
And the dash before the seven? Does that mean: open minus seven days? What does that even mean? A restaurant for time-travellers?
The Apostrophe Protection Society should be informed.
Actually, thinking about it maybe the sign should just be corrected.