When grading a quiz, a "Restrict to" drop-down control allows you to restrict the list of users displayed to those who have taken or not taken the quiz, received a score within a specified range, have attempts in progress, or have previewed the quiz. However, when you make a selection from the drop-down, the list of users displayed does not change.
The list of users does not change until you press the Search button that resembles a magnifying glass ( ).
This is a known issue.
After making a selection with the "Restrict to" drop-down, press the Search button and the correct list of users will be displayed.