They don't have a couple of scraps left on, and the next roll in line has not been plundered of its first few squares. The roll is exactly finished.
I can think of three possible explanations.
- Yer modern Tesco toilet roll is precisely calculated by computer to match the toiletary needs of a family of three (with a complex algorithm that caters for the needs of the occasional visitor too).
- This person likes to round up to the nearest square.
- This person prefers to suffer mild discomfort rather than go to the bother of opening up a new roll to finish off what the old roll began.