I read that as the size of file it's transferring so each operation would be bigger and therefore slower

It measures PutObject[0] performance across different object sizes (1, 8, 100MiB)[1]. Seems to be an odd screenshot of text in the terminal.

[0] https://github.com/good-lly/s3mini/blob/30a751cc866855f783a1... [1] https://github.com/good-lly/s3mini/blob/30a751cc866855f783a1...

Oh, I see my mistake. Those are payload sizes not intance sizes in the heading for each table.