What does CCYYMMDD date format mean?

It's just another way of writing yyyyMMdd.

The CC part represents the century, while YY is the two-digit year.

It means yyyyMMdd, as in year (4 digits), month (2 digits, leading zero) and day (2 digits, leading zero).

So the ISO 8601 date 2014-01-05 is represented as CCYYMMDD as 20140105.