Its more a case of understanding what is going on with the data, what the scan is telling you is how it has interpreted the pits and lands on the disk ‘this time’ and the amount of error correction needed to give the result the drive ‘thinks’ is right, or the same as what was put on to the disk in the first place.
The result will be different every time you scan, the difference between a good scanner and a ‘bad’ scanner are how much the results differ each time.
With my NEC the results could be almost another disk each time, if just from the results because there is no real correlation (I think) between each run, but my LiteOn is very good (again IMO) because I can see the same problems on a disk each time I scan it at any speed.
You need to read the sticky posts at the top of the media testing forum as its not a simple subject, I learn something almost every time I read this forum (which I like). If you only read one thread try the Precision, accuracy, and reliability of disc quality (PI/PO/jitter) tests its a long thread but will give you a good understanding about the subject and how much the interpretation of the scan by you and the drive your are using means so much, its often not just a case of this is a good scan, so it must be a good disk and the reverse.