The highest value on there is 9.6 and the lowest it went to was 7.6 which does sort of indicate a problem. On a good line you should not have a variance of more then 0.5db.

Unfortunately the way the industry works it's very hard to convince your ISP of loss of speed unless it's drastic or unless there is an obvious problem with your line. I recently lost 3MB and Sky have shown no interest what so ever in explaining or fixing it.