It's been about two years since I coached or judged men's in the US and while some things were modified, they still followed FIG rules for scoring. If they still are, then they count the 8 highest skills by element group and not just the 8 highest skills. I'll try to explain the best I can. Let's use a ring Routine as an example. There are four elements groups now: EGI Swinging elements, EGII strength elements, EGIII swing to strength, and EGIV Dismount. So if the gymnast has total of 8 c/d value skills from EGI, EGII, and EGIV but only does a a/b value skill from EGIII, one of the c/d value skills is lost and the a/b value skill is taken because the judge has to count at least one skill from every EG that is preformed. This also doesn't take into account that you are only allowed so many skills per element group in a routine as well. In the example below only skills 2-9 would be counted because each element group is counted first and then each remaining skill is counted for difficulty so one of the C value skills would be left out.
1. EG III - Back Uprise Cross - C
2. EG I - Back Uprise to Handstand - C
3. EG I - Yamawaki - C
4. EG I - Jonasson - C
5. EG III- Uprise to Support Scale - D
6. EG II - L Sit - A
7. EG III - Molinari - D
8. EG I - Honma to Handstand - D
9. EG IV - Double Back - B
You used to see this a lot when there were five elements groups, because there was one element group on each event that was just harder than than the others. Especially for the younger guys.