Help rationalizing a business' valuation method

Trying to rationalize something, I've been eyeing a business that has been pretty up and down with regards to cash flow and revenue. Has been listed for at least 2 years. What im trying to wrap my head around is the multiples. At one point, when the cash flow was high the multiple was low (as compared to...) when the cash flow low, they took an average cash flow (over 3 year period) and raised the multiple. I wish i knew more about multiples so i could better understand whats going on with seller and intermediary.