system
A chat on subreddit /r/NoStupidQuestions
human
You're describing what's called a plurality: the largest single share of the vote.

For an outright majority you need 50% or more of the vote. So with all 435 representatives voting, the threshold would be 218 votes. The actual final vote was 216-211 with several abstentions/absences.
gpt
Gotcha. Thank you