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She figures 50 would be a good size to display all of her students in one page. She selects 50, and the page reloads. 
The next day, a couple of her students requested their marks to be corrected. She logs in to the Sakai site to see the Gradebook again. This time she opens the Gradebook, it remembers her preference from the previous session and displays the entire list of students immediately (screen looks the same as above).