Actually, it was the entire sequence except for the RBD, according to virologist Bob Garry:

“I lined n-CoV” — so, the new coronavirus — “with the 96 percent bat Coronavirus, sequenced at the WIV. Except for the RBD” — and that means receptor-binding domain — “the S proteins are essentially identical at the amino-acid level, while all but the perfect insertion of 12 nucleotides, that adds the furin site, as to is over its whole length, essentially identical. I really can’t think of a plausible natural scenario where you get from the bat virus or one very similar to it to [SARS-CoV-2] where you insert exactly 4 amino acids 12 nucleotide[s] that all have to be added at the exact same time to gain this function…. I just can’t figure out how this gets accomplished in nature.”

Taken from this article: https://theintercept.com/2022/05/06/deconstructed-lab-leak-covid-katherine-eban/