This was a very significant scene as we see Samuel (Friday) first walk into town and his reaction was really devastating to all the readers as he states how not a single soul looked at him or even bothered to notice him.
This was significant to readers and Samuel (Friday) as this is first interaction with selling and auctioning people which is a really cruel thing to see all the slaves sitting in the barn not having a single voice or say about what to do.
Samuel (Friday) here first witnesses how the auction and everything is about to take place. He notices how its a cruel and inhumane thing for the white people to do
Samuel (Friday) was very surprised by the fact that so many people show up to buy and get slaves and how its seems so normal as if there is not a single thing wrong with it.
Samuel (Friday) here talks and realizes how it all got silent and everybody was just looking at Milly but as the readers we understand why this happened and how exactly Milly was looked at. This was also crazy because she sold for 2000 just because of how she looks and her age.
This is probably the most significant part as we see Samuel (Friday) actually get sold and bought by a little kid named Gerald who is about the same age as Friday. There could be many reasons as to why Gerald bought Friday but that is still very sad as Gerald is only a kid and he is buying slaves.