Everybody in the car is excited. Each "seat is filled with excitement." Except for the author.

Student or Learner
Hi there,
I don't understand the underlined part in the following sentence, could anyone help me out?
Thank you very much in advance.
"My father says that he was looking at some RVs in the paper the other day to rent for August. He keeps talking about it and lamenting prices and filling every seat in the car, except mine, with excitement over the trip he and Mom had planning for last August."
Everybody in the car is excited. Each "seat is filled with excitement." Except for the author.
I think this trip is due to take place in the future. In his father's imagination, each seat in the car is filled (someone is sitting in it) and everyone is equally excited about the trip. In reality, the writer (who will sit in one of those seats in the car) is not excited about the trip.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
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