A recent change to Period View, apparently to speed up the display, means that when Period View displays it now shows "0 pupils" on the summary bars for Absent, Present, and Unregistered, see screenshot.
This is a retrograde change because if one want to see a registration session summary, you have to expand each bar to show the detail before the correct pupil count is shown. This means that the task requires extra clicks and takes longer than it did before, even if the initial display is faster!