Here’s a few example scans I stole from the drive reviews here at CDfreaks, I can’t be bothered to post my own scans.
A typical scan of a good burn, should play back fine with most DVD players (except those that are not tolerant of -R/+R media in general) and the data can easily be extracted by a drive in a computer:
A scan of a disc that isn’t as nice, but will probably still play back fine in most DVD players but may skip on occasion on pickier players at the trouble spots. The dips in the scan aren’t severe enough to cause problems with most players in all likelyhood, though, as players only need to read the data at slow speeds.
Another similar result:
A poor result, the disc will skip/freeze/etc. on all DVD players in all likelyhood. The test starts out fine but the test has to slow down and then ultimately cannot even reliably read from the disc.
Here’s a gray area disc, the disc will probably read back OK in most DVD Players until it reaches about 4GB, then it will likely begin skipping/freezing. This is a typical looking scan of cheap media where PIF errors rise at the edge of the disc.
While technically any disc that can complete the transfer rate test is capable of having all of its data extracted, most people would consider anything less than a near perfect transfer rate test a bad burn. Very slight dips are fine, but large dips are cause for concern. Also, a transfer rate does have some advantage over a PI/PIF test in that it will show the genuine ability to read back a disc. You can have a disc with fairly high PI/PIF errors and still read back perfectly. You can conversely have a disc with great PI/PIF numbers and have some readback issues, whether it be because of high jitter rates, poor reflectivity, etc. BTW, your scan is fine, it appears that your burner simply tops out at 12x read speeds. And the first scan you posted is the speed that the disc was burned at, dips such as those in that test are normal as the laser adjusts.