Help explain instructions?

I am knitting Cyochin sweater and am stuck understanding what it is telling me to do:
this is the pattern [http://knittingfever.com/wp-content/kfi_system_files/free-patterns/KFI_free_pattern-159452.pdf]

Shoulder armholes RSF
Beg with purl row st. st. 7 rs.

I think it says beginning with purl row then what does the rest mean? Do I do stocking stitch on my purl side and do it for 7 rows?

Yes. Purl the first row, then do stockinette for the next 7 rows. Stockinette when you’re knitting flat is knit a row then pull a row. Since you started with a purl row your next row is probably a knit row.

Ok so I purl on the purl rows and knit on the knit rows a toatl of 7 times? I started with a knit row.

Yes, stocking stitch is knit and purl rows alternated, so knit a row, purl a row, knit a row, purl a row etc. If you had started with a P row, 7 rows would look like this:
P
K
P
K
P
K
P

Yours will be the other way round as you started with a K row so maybe add an extra row in? (This would not be in the pattern as it is an extra row but won’t make much difference to the finished garment.) That way you will be following the pattern again.

Great, thank you!

Thanks for the explanation.