A Greek notice with a limited exception

An original Greek notice reads: «Η βιβλιοθήκη είναι ανοιχτή από Δευτέρα έως Παρασκευή. Την πρώτη Δευτέρα κάθε μήνα παραμένει κλειστή. Το Σάββατο λειτουργεί μόνο το πρωί». One learner says the library opens every Monday because Monday appears in the ordinary schedule. Another copies Saturday’s arrangement to Sunday, although the notice says nothing about Sunday. A third combines the ordinary rule and its exception. The task asks what is established and what remains unknown. No real library, holiday policy or exact Saturday closing time is supplied. This is a newly composed classroom exercise, not an actual institutional announcement. A useful response should preserve the day, exception and limiting word μόνο rather than select an answer because it repeats a familiar noun.