The final column isn't LoC written that day; it's LoC in total. Friday was spent refactoring (what we in the old days called "rewriting", before the hipsters made it cool); taking the code that was already working, and making it smaller, lighter, better.
> what we in the old days called "rewriting", before the hipsters made it cool
Calling it refactoring dates back to at least the early 90s[1], which I'm pretty sure predates "hipster hackers." If anyone "made it cool" it was probably Martin Fowler[2].
