How many dreams do you have per night?
Try this:
1. Calcualate the the exact date of 30+ days ago (e.g: today is April 15, thirty days ago was March 17).
2. Go through your dream journal and count how many dreams you had since that date.
3. Divide how many dreams you had by the total days

Example:
I had 24 dreams over the past 30 days, therefore I have 0.8 dreams every night (avarage)