This read-only PerfTotalCount reports the count of frames received with CRC checksum errors on the DSL port, scoped to the most recent rolling 24-hour period ending at the moment of the poll. Operationally, CRC errors are a direct measure of line-quality problems, since they indicate data was corrupted somewhere on the copper loop. For example, an admin building a weekly line-quality report pulls this rolling 24-hour CRC-error total each day at the same time to get comparable, full-day figures.