Well I think you are nearly there

The Bumblebee is 2 gene, so Pastel and Spider. Since when breeding it need to past 1 allele at each loci, yes a bumblebee can past both pastel and the spider gene at the same time. But it can also pass the normal gene that is at the same loci as the pastel or the spider gene.

That's why the first row read as this : PS Pn nS nn
These 4, are all the possibilities of the genes it can pass when breeding.

I think you understand it now