The lines at the top are changes that represent improvements but they're not required. Example: one of the changes replaces the word "abroad" with the word "strolling", because I'd said that people were abroad (in the sense of out and about) some eight pages earlier and the repetition jarred. Other changes are to phrasing, so "Chrissy wondered" might become "wondered Chrissy". That's the kind of level these are.
The three lines in the middle are for changes to the hyphenation. They're also not required, but will make the layout of the text look a little better.
The nine page numbers in two columns to the right, just beneath the top lines, are underlined. These are show-stoppers: changes I really do have to make or I can't release the book. When I can read through the book and find none of these, that's the signal that it's ready for publication. I was rather hoping it would happen this time, because the 150th anniversary of the Paris Commune is almost upon us and there's a faint chance that people looking for novels set in the period might accidentally find Lizzie Lott's Liberty in their trawl. The nine changes that fall into this category are: a description of an action that's physically impossible; an action that only works if a room has a layout that it doesn't; use of the word "gently" twice in the very same sentence; missing out the word "be"; changing "she'd had questioned" to "she had questioned"; using a nickname when a formal name should have been used; missing a space after a dash (" —" instead of " — "); missing out the word "her"; using the wrong nickname for someone who has two.
The notes at the bottom are reminding me to re-check something. Hmm. I guess I'd better do that!
I can certainly see why so many professionally-produced books make it to the shelves with errors in them.