Originally Posted by Darkheart 
This one was around 300 MB on Steam. The one before made you re-download the complete game.
That's weird, we didn't have that with the previous patch on GOG, but it was released 2-3 hours later. So it really depends.
It was really a big issue with BG3, a few updates were 60-70 GB. Then you had to keep 3 times that space free on the same disk because of the download, the new and old version of the files when the patch was being applied… Thankfully Galaxy added an option to specify the location of each operation, which made it more tolerable.