Every number is Russ’s own rating out of 10. Russ has previously stated that he never scores in sponsored videos, so the food he reviews carries no applied pressure or bias.
One of the best Japanese low sugars he's had; only slightly perfumey and too sweet.
Russ calls the lychee Kirin an easy 9/10, tasting like fresh real lychee with no aftertaste. It misses a 10 because it's a little perfumey and a bit too sweet, kind of like Turkish delight.