Sea snake tutorial problem

In the sea snake tutorial, we apply (($NPT-$PT)/$NPT)+0.2 in the ?gSweep?h scale field.

The $NPT is 68 and the Sweep scale is a constant value of 0.258824, then I got the value of the $PT (63.99968 if I did the right calculation).

1.My question is where can I find the $PT (vertex number) without doing any calculation.

2.How does this function work?

3.Its value is a constant number, so how come we can get the different scale of the sweep?

Thanks for any replying in advance. :roll:

Whoops :shock: