My eyes focus at multiple depths- which is the right one?

So I inherited my dad's super 8 camera, and I thought it might be fun to shoot some film for a music video for my band on it.

Now, it has a focusing ring on the lens, but i have the problem that the image looks focused to me at a range of positions. Like, I'll bring the image into focus, and then I'll adjust the ring, and everything blurs out for a moment, then my eyes adjust and everything snaps back into focus, then I adjust it again, and again the image in the viewfinder blurs out, then my eyes adjust and it snaps back into focus again.

In my kitchen this morning i was able to focus my eyes with the focus on the camera set anywhere between zero and infinity while zoomed out, and between 2 and 6 feet while zoomed all the way in (if im reading the numbers on the camera right). Which one is going to look correct on the film?