How does this work?
The Paragraph spin size, ie paragraph spintax group size works like this.
For each paragraph how many extra paragraphs should it add to it as a spintax group.
P. spin size = 1
Paragraph1P. spin size = 2
{Paragraph1|Paragraph2}P. spin size = 3
{Paragraph1|Paragraph2|Paragraph3}etc…
Its a way of creating more variations in your article at the paragraph level.