Change Details

Just noticed on English Wikipedia that a page I am watching has 5 changes today, with an overall byte count of -2389 but individual byte counts of 265, 265, 286, 209 and 625. These obviously don't add up! Note that I'm using the option to group edits to a single article. If I can figure out how to upload an image, I'll add a screen grab of the relevant portion of my watchlist. No idea what might cause this or how to reproduce it, sorry.