CPD is directly related to the Cunningham Chain Length parameter in your config file.
It can be changed to 9 or 10 for stable results for current or older cards.
Just remember to change the corresponding sieve layers number.
Having 10 will show lower CPD with one or two digits, but won't affect your chance to solve blocks. I've tested this over a period of 5 days.
9 can show CPD with two or three digits, again not affecting your chance to solve blocks. I'm using 9 as a standard.

Have a look at what the miner uses.
Most people seem to be using 9 (the higher CPD) when posting results for reference cards, so try change yours to 9 to compare.

*Tip, when comparing, use 1 card at a time, since this algorithm is heavily reliant on CPU threading, which can easily skew your numbers due to a bottleneck with more cards.