I would guess the numbers on page 5 are batting averages. The order of leagues (the US's Major League Baseball, Japan's Nippon Professional Baseball, and Taiwan's Chinese Professional Baseball League) suggests what most would interpret as successive 'demotions' with respect to the level of overall skill. Ordinarily one would expect the batting average of a player making such moves to increase as those occurred, since the pitching would be less challenging. A .250 is generally close to the MLB league average most seasons, but depending on other aspects of the player's game could be insufficient to keep them on a team.
Thanks for the chapter, and for sticking with this series - Kumeta's current art style is so fantastically unique, and his humor is goofy in a good way. I enjoy each of the chapters of this work, and appreciate having such an excellent translation!
