That's my fault for not phrasing the field correctly. It really should be "We need this in X days", and not "This is X days of constant work", which is how most people are interpreting it.

Even then, unless you complete this project in 10 hours, it's not worth it. And by "complete" I mean completely done, no more back-and-forth, no more bug fixing, a complete sign-off. I almost never see it go perfectly like that, and that's why I'm hourly. Want me to fix the color of that button six times, because you feel like a designer? No problem, but you're paying for it.

The requirements are so vague it's hard to tell the number of hours they expect in that fortnight.

Fair point. I am also working on this. I didn't want to necessarily have people copy/paste their entire spec here, only a pitch.