C1 count will more often than not, vary slightly each time you run a BLER check on the same cd, even in the same drive.
The file test and scan disk verifies the data by block structure. As long as everything is read it will show 0 errors. You could have thousands of C2's and still get a perfect data scan as long as there are no CU's. I was just running a null test on a clients pressed cd with my PMCD copy and decided to check it in CD Speed after running a BLER check in Plex Tools Pro. C1's = 1236, avg per sec was 1.0 and max 14 per sec, in PTP, CD Speed file test and surface scan all green 0 errors. I tried to do a BLER check and it said Error failed to initialize the disk. I tried it on all the CAV speeds and same error, it wouldn't go into the C checks. Nope, I'm not happy with CD Speed, it's a waste of money if you have Plex Tools as far as I'm concerned.