Subthreshold slope (which often is not monitored or
controlled), mV/decade. Your VT is the mV, 0 is the
minimum gate voltage you can see in normal logic beds.
So you can simply figure how many decades down from
I(@VT, W, L) you are, and the math will show you why.
You can use a dummy value for insight, or a foundry
value for more realism (but good luck getting a worst
case PVT value, consider yourself lucky if the nominal
modeling of it has a basis in fact).