minTopValue not working

Hi there,
Thanks for making this great library. It's works mostly, but I'm not able to get minTopValue to work.

As stated in the README:

> so if at least 100px are in viewport, we mark element as visible.

I've set minTopValue to just 10, but the element goes hidden as soon as 1 pixel goes outside the containment.

I've even tried it in the codesandbox and it doesn't work: https://codesandbox.io/s/jl8r92z0lv

Anyway I can achieve this? I basically only want an element to update as hidden if half of it is outside the containment.

Thanks!