They mean 125um = sqrt(a*b), where a is the Planck length* and b the size of the observable universe (I didn't verify). Implying, 125um is some sort of middle ground.
*Often said to be the smallest length with physical meaning.
In our current understanding of the world (quantum mechanics), the world is inherently probabilistic ("random", not deterministic) in the microscopic realm. There are differing opinions among physicists whether or not there could be a more fundamental layer of reality beyond this, and if so, whether it would be deterministic. Notably it could be said the mainstream view is that reality is not deterministic.