You mean some of the blobs should be unfilled (ie open) and some filled (ie closed)? Yes, strictly speaking, as is clear from the time periods given with the function, we should include the point at the left-hand end of each horizontal line and exclude the point at the right-hand end. The examiners don't seem too bothered about this nicety on the graphs - the most recent question of this type (September 2016, Q6) has the same sort of graph.
