I think he would probably know that duds are a thing - its pretty easy to know within a few days if eggs are viable or not with candling. But knowing that doesn't mean it wouldn't hurt, that he wouldn't feel like he failed even if they were never fertilized in the first place...

I'm with Tora on egg size. Usually for numbers I take a glance at the average clutch size for a normal turtle. Usually it's somewhere around 30-50 across species. Which... that's a lot, lol. So I divide that in half then give a random amount of duds. So anywhere from 2-8 + duds for a bigger belly <3