Good question--yes you can. Once a number is called, players will have 2 days to start a piece that satisfies that prompt. So you could get Wednesday's prompt and think of ways to combine it with the prompts from Tuesday.

Or you can keep adding to the story based on each day's prompts. Mirach did that last year: wrote a long story where each day's addition was determined by the day's prompt.

Pretty much as long as something new is being created for the prompt, it will count. We're very easy. :)