In Stranger Than Fiction (2006), I encountered some measurings are shown, which are actually not related to the plot of the movie. What is the use of showing them?
The "measuring" is showing the calculations around him.
He's depicted as being obsessed with counting and measuring stuff... He counts his toothbrush strokes, for example... which is why he's an IRS agent. The intro text from the book being written about his character is:
Harold Crick was a man of infinite numbers, endless calculations, and remarkably few words and his wristwatch said even less.
Similar measurements are seen in the opening of the film:
So, when he's in the lavatory with Jules, his brain is measuring how full the three soap dispensers are. The farthest one is a little under half full, so 49%, the middle one is 93% full and the closest one is 73% full.
The entire film is about Harold's head so anything you see on screen is something he's thinking about.