As an example, let's say your current average number of transactions per month per customer is 3ǌ. Which says on average each customer does business with you 3 times each month. You could calculate how much more profit you would get if you could increase it to 3Ǒ. And I can tell you that would probably be enough to meet your plan. And if that did generate enough profit, all you would have to do is maintain everything else; sales, expenses, labor, average dollar sale, etc, and then just figure out how you could increase your transactions from 3ǌ to 3Ǒ. Maybe it could be with some type of promotion that would get customers to come in more often.
When writing a business plan you sometimes end up locking yourself away. You might have unique ideas which lead you to seek some isolation and secrecy, or if you are going to be a sole trader you may only have one person to consult namely yourself. But it is fantastic to try and get broader input on your business plan _ whether from a professional, or simply from friends and family whom you trust. I say that because of course you need to be careful with commercially sensitive ideas, as you do not want to pass your plan on to someone in the pub who then starts your idea before you across the road.