I ran across the sentence written by an American guy in his published book, saying
Could you move one seat over?
Do you alternatively say
Could you move over one seat?
I ran across the sentence written by an American guy in his published book, saying
Could you move one seat over?
Do you alternatively say
Could you move over one seat?
I would suggest that both are idiomatic. If you analyse each of them they can seem like they are a request for the seat itself to be moved!
I would say that the second is the one which is correct:
Could you move over one seat?
This request identifies the subject, the action, and the direction/measurement in that order. You want the person ("you") to "move over" by "one seat".
Could you move one seat over?
Under scrutiny this version sounds more like you are asking for a seat to be moved because it groups the seat and the request to move. But as I said, it is idiomatically used and would almost certainly be understood.