The outdoor table spaces circled in red are always occupied whenever I pass by, perhaps because they are close to one of the dining areas and located on one of the busier sidewalks in school. The other two, circled in orange, are sometimes occupied, especially on sunny, calm days. During windy or cloudy days, those places might not be occupied since the wind could be blustering around that corner.
For some reason, the table circled in blue has never been observed occupied by me. I suspect this may be due to its exposure to the sun for only a very short time slot during the winter, typically in the morning when the campus may not be crowded enough.
*The conclusion may be inaccurate because winter is not a favorable time for outdoor activities, and my observations were usually made around 1-2 p.m., when the “never occupied” table was covered in shadow, thus making it less favorable as a winter outdoor space.