When I sync OneNote on my computer with OneDrive, does it just transfer changes, or the entire file (or page or section) in which changes have been made?

I ask because my internet bill shows a drastic increase in data uploads, and I'm wonderinng if it's caused by the fact that some of my pages in OneNote have a lot of videos. If I make a text change on one of those pages would it just upload the text change on sync'ing, or the entire page?