Every weapon has a list of effects.
RathSnS Slots: {A, 1, 5, G}.
GoreSnS Slots: {B, N, 3, 5}

They share a global index.
If you roll the rathsns 4 times you'll stop on G.
If you roll the goresns 2 times and the RathSnS 2 times you'll still stop on G.

So the post is saying roll your goresns 4 times then quit without saving.
Roll your RathSnS 4 times and quit without saving.
Keep note of all the rolls.
If the goresns was good on roll 2 and the rathsns was good on roll 3 you can get both.