That's for guys in juniors. The first year can slide as long as they go back to juniors before 10 games are up. Europeans might fall under the same category. The college guys are different, I believe. It may have something to do with their age when they sign their contract. Z is 18 now but will be 19 in a few weeks. I'd have to look it up. You can probably look up Quinn Hughes and I imagine Z falls under the same category.
And yeah, you're right. You can burn a year off the ELC without having RFA status bumped up by a year. Believe that is where the 10 games comes into play. So if it's what I think it is, as soon as Z plays one game, he burns one ELC year, but can play up to 9 games before he's considered to have played a "pro season." That is what affects RFA /arbitration status.