I'm not counting those, I'm counting vacation time. Lets say you get X vacation days right now, this means that you get X/5 weeks off. If the workweek becomes 4 days, while you're still getting X vacation days, the number of weeks off you get is now X/4. This is relevant because vacation time is almost always taken in multiples of week-long periods (ie. "Next year I'll be taking 3 weeks off in August, one in December, one in January and one in June").

Ohhhh I see, you're talking about how many vacation days it takes to fill up a whole work-week, like the commonly seen benefit of extending golden week's 3 days off into a full week using only 2 vacation days. Gotcha.