I understand what you are trying to do with sales projections but heres the problem.
1. Are you basing it on a food court or in-line store?Red Rock Chili Company offers both and this can alter projections.
2. Would you base these numbers on a (A) location with a high demographic average income area or middle of the pack?
3. How large would your restaurant be?Red Rock Chili Company restauants can be as small as 600 square feet up (food court) to 1600 (in-line).This can alter sales projections a lot.
4. There are other small factors to but the point is you have to look at it from all angles before you can put a hard cap.As for me I visited several Red Rocks until I found one in a city that was close to the same demographics as the city I planned on putting one in.Then I counted how many customers a day they had for several days.When I personally felt like the numbers would be similar I made the decision to buy.If your rent is reasonable it really helps to not have to have a huge volume.I hope this helps.
Northern California Area Developer for Red Rock Chili Company (WWW.REDROCKCHILI.COM)