I've seen low to medium rates of C1 errors on different brands of discs I've burned in the past with few if any C2 errors. Nero DVD-CD speed was used for the tests. The upward green line is good on all of them & the discs are fine for both data & audio. I just wonder if I should concern myself with C1 errors (as I do C2 errors) or just forget about them. A lot of C2 errors (or downward dips going too far) & I reject the disc!