Booking a 40 minute connection in SEA is NOT a good idea, especially when there isn't another flight to EWR for 7 hours, and the next flight could easily be full.
If you are lucky, you will arrive into N from PDX and leave out of N to EWR, but you could just as easily arrive into C and leave out of N. The tram from C to N isn't that fast, despite what AS would like us to believe.