For your information, each time the children borrow the books, the 2 books will be put in a yellow bag together with 2 book reports and a tick-tock book. The tick-tock book is yours to keep, while you have to return the 2 borrowed books and 2 book reports. Teachers will stamp on the book reports.
As regards the date of return, it will be 12 days after borrowing, e.g. books borrowed on 22/9 (Wed) will be returned on 4/10 (Mon). Then the kids will borrow another two books on 6/10 (Wed). The dates may vary from class to class, though.