question about scrog net

Hello! I my package just came in and I thought I had ordered 2 scrog nets but it appears to only be 1. Will I be fine with using just 1? if so how high should I put the net? right now my plants are about 12"

I tend to use two layers of trellis.
The first at 12-13" and a second 12" above that.
I veg the plant for 4-6 weeks while I top and manifold to produce 6-8 main colas and flip them to flower once they reach the first net. I weave branches through the first net during the stretch and then let the new growth reach towards the second layer. The second layer is just there for support as the colas fill out.

do i need to order a second one? would i be okay just using this one? or you think its a necessity

if i didnt order a second one and was fine just using one. how high should i put it? around 15-16?

This may help you visualize what I'm trying to do with the netting. He uses stakes but the result is the same.
A single will get it started but I've found that a second layer about 12-14" above the first helps support the sea of buds that form.