english

I would assume "page 1, page 2," etc. I do not have the context you are looking at, though, so it's hard to tell from here.

p1 sn v

These are Shurley English abbreviations.

pattern 1, subject, noun verb

http://www.google.com/#q=shurley+abbreviations

i do not understand how to get the answe

answer

Study your English materials. Study the link I posted.

Besides, I gave you the answer.

This site explains some of the vocabulary, including sentence patterns.

http://images.pcmac.org/SiSFiles/Schools/AL/BaldwinCounty/JLarryNewton/Uploads/DocumentsCategories/Documents/Shurley%20Grammar-%20Quick%20Guide.pdf

so like this ?
the weathered old raft was drifting downstream by itself.

it is p1?

Yes, it's sn v. It's pattern 1.