yebbut, why make extra work for themselves by setting the minima
that low
If I was in their HR dept, I'd set the minimum hours such that I'd only need to deal with what's required in the nearish future plus maybe a 200% extra allowance to cater for change-of-minds, dropouts, unsuitability, etc.
As C. Northcote Parkinson says in "Parkinsons Law" "The short list"
To choose between three hundred people, all well qualified and highly recommended, is not really possible. We are driven therefore to conclude that the mistake lies in the original advertisement. It has attracted too many applications."