I'm about to query an agent who asks for a query letter and the first ten pages of the ms. My first chapter runs to 11 pages and a bit. I don't think it would be a deal killer simply to send 10 pages as specified, but would rather send the whole chapter. Would that be a deal killer do you think?
Oh please, you'd rather send the whole book if you could!
That's the whole reason query guidelines specify the number of pages to include in a query.
If the agent asks for the first 3-5 pages, you should send 750-1250 words.
If the agent asks for the first 10 pages, you can send 2500 words.
There is a wiggle factor here is so you don't have to end mid-sentence (do NOT do this, it's maddening)
Try to end at the end of a paragraph.
And of course, ending at the close of chapter is ideal.
BUT you can't send 17 pages to do any of that.
750-1250 words +/- about 10% or 125 words
2500 words +/- 10% or 250 words (which is about a page)
So 11 pages is probably fine.
I don't know anyone who actually passes on a project if you send 11 rather than 10.
I do know a whole raft of agents who are annoyed when you send the whole manuscript with a query. And it doesn't do you any good, I won't read much past six or seven pages. (I ask for 3-5 pages in the query)