The little oval leafs that come out first are called cotyledons, they don't count, the next set of leafs are the first true leafs but don't count either (as the plant will drop them)
Definately counts as the first node, doesn't matter if the plant retains them or not. The issue is where dormant buds reside, and they are located in the petiole's axis, the future main colas. Above ground and those dormant buds differentiate into foliar output, below ground and they differentiate into root output.
Speaking of retaining leaves.....see this plant, notice the tiny leafsets at the bottom, node #1? If I can retain such juvenile leafsets, you can too.
In fact, I think I see the cotyledons still hanging on this plant and it's about 2 months old if memory serves me correct. My cross - O. Haze X C99. The cotyledons are commonly called "seed leaves". Not really true leaves but endosperm used to provide the embryo nutrition.
Good luck,
UB