DVD error correction is based on 32kB blocks of data divided into rows and columns, one such block is called an ECC block (ECC: Error Correcting Code).
A 1 ECC scanner will report the (correctable) parity errors and failures per single ECC block, whereas an 8 ECC scanner will report the sum per 8 consecutive ECC blocks.
It’s always possible for a program to calculate the sum over 8 ECC blocks given the values for each single block, but the reverse is not true.
If you don’t belive me, then please tell me which eight natural numbers have the sum 13?!
This means that in a sense the 1 ECC scanners are more precise, and the maximum PIF reported by a 1 ECC scanner and an 8 ECC scanner will usually be quite different (up to a factor of 8 higher, but statistically speaking it’s more likely to be only 3-4 times higher).