The first pass is for plot, or for the argument. The second pass is for the sentences that only show up once you stop chasing the ending.
I used to treat rereading as a failure of the first read. Now I treat it as the actual read. The first time through, I am mostly asking where this is going. The second time, I can ask how it is built.
That second question is the one that changes how I write. A paragraph that felt smooth on Monday turns out to be three ideas hiding in one breath. A line I underlined for the feeling turns out to be precise.
What earns a note
If a page survives a second look, it earns a note. If it does not, I let it go without pretending I have a take. The notebook stays thinner that way, and the notes that remain are the ones I can still use a month later.