I was confused as well. I think looking at this will make it clearer: https://en.wikipedia.org/wiki/List_of_Big_Windup!_chapters
Basically if you look at the description for volume 16 it says it includes chapters 29-30 which are Afternoon chapters 59-63 where Afternoon is the magazine it's published in. I'm guessing this inconsistency is due to the author breaking her chapters into parts when publishing them.
So chapter 30 is not Afternoon chapter 30. It's likely Afternoon chapters 60 and 61 (it doesn't include 62 and 63 btw cas chapter 30 is actually incomplete). That's why it seems like the chapters jumped from 30 to 50 something. It's actually that they stopped uploading the chapters as 25.1, 25.2, etc and instead started uploading them by their Afternoon chapter number.
So you should continue reading at chapter 62 since it's actually Afternoon chapter 62. Hope that wasn't confusing x.x
Btw if you go and look at chapter 53 you'll see that it's actually either 25.3 or 25.4
I don't understand. It's chapter 30 and then it goes to chapter 53? Are there some chapters missing?
Someone said below that after read chapter 30 you should go to chapter 62, because chapters between them are not in order, but these chapterss (53-62) are they reupdate (and renamed) in order? I'm confused.