I think it's probably just some youtube viewer calculation nonsense. The fluctuation seems to have been over about 5 minutes, and it's been a pretty normal curve outside of that:I don't want to detract from the experience but I'm beginning to wonder if someone's botting the graduation, the numbers are yo-yoing in the past few minutes from mid 600K to mid 700K down to mid 500K and back to mid 600K.
(I guess it could just be youtube being youtube, though)