A bit more detail: the "min" and "max" determine the smallest and largest gap between threads, so effectively larger numbers mean thinner threads. and thus, more transparent fabric.  A 0 means no gap at all, a 1 means the thread effectively disappears. But there is some random variation between the min and max, so in effect you only see the occasional stretch of disappearing thread. The get actual holes you need to go higher than 1.

Here is a sequence of renders with the min at 0 and the max at 0.3, 1.0, 1.5 and 2.0 respectively:

-- I'm not mad at you, just Westphalian.