Good writing is not reducible to numbers; the word count for the expression of an idea can’t always (or even usually) be determined in advance. Ideas fit all kinds of containers, some small, some large, some book-shaped, some made of 1s and 0s. When I aim for a specific word count (or ask students to aim for a specific word count), it’s not because I think there’s something intrinsically meaningful about lining up a certain number of words. It’s not because 500 words amassed are somehow better than 25. But knowing the size of a container can give us a sense for what and how we might fill it. 500 words looks different than 25 words, and 500 words feel different coming out of our mouths or fingers. For the same reason, it’s sometimes (but certainly not always) useful to pre-determine the genre for a piece of writing, the shape of the container, before sitting down to construct it.