I wrote a short paragraph (a few lines) for two of my risks. On the third risk, I wrote almost a page. It was a fun topic to write about, so I wrote a lot. You don't need to write an essay though. They wound up asking about the third risk on part 2 and I wrote a small essay there too!
I have a page and a half of assumptions. I erred on the side of listing everything as an assumption rather than leaving something out. It wasn't an effort though as I wrote them as I went.
My assumptions list is close to a page.
My risks are only 3 (in fact I am stuggling to gill the 3rd). However, for one of the risks, I am having fun writing 3/4th of the page. For the other 2, just 2-3 lines.