Unless it's changed - the questions at the end of the application had a min 250 and max 500 words. I asked a question about this, and was told applications get rejected if people don't meet them. Again, it could've changed. But if there's a word limit specified on questions within the application (i.e. why do you want to work for us?) I'd recommend keeping to them.
I used MS Word to type out my answers and checked for typos and spelling errors. There's also websites out there that you can paste your replies into to check your count.