Each vertical column contains the set of ratings of one respondent. It would be reasonable to expect some consistency in these responses. Some difference in responses could be expected between these two. With a sample size of 21 it would not be a good idea to make too many generalisations from the data. The results are interesting and show support for the NetLesson concept.
Any wider conclusions are on shaky ground.
I welcome others to interpret the data and email comments. I will post them here for others to see. The single most difficult point for some students is the transition from reading material in books, to reading material on screen. It is not easy, especially if the material is even slightly abstract. The students have difficulty with concentration and comprehension.