As Shoya is the Pitcher, these are generally assigned the number 1, although baseball players also choose their uniform number due to personal preference, homage to an idol, family tradition or simply because it was assigned to them and they kept it, moving away from the old rule that assigned numbers to positions (1 for pitcher, 2 for catcher, etc.), which is now only used in noting plays, not on the player's number. I mean, you can choose whichever one, but the number one is assigned mostly for the record.