You stuffed up the math, its 1/13 of a second per puff! The second counter has gone around the clock and started again. Or maybe its actually minutes.
I've been known to mess up a math problem but this is (pretty much) what I am getting too. To explain I'll use some simpler numbers. Suppose he had 10 seconds of run time and 5 puffs. Well, if you puffed for a total of 10 seconds and it took you 5 puffs to get there then you could say that you averaged 2 seconds a puff. Because 5 puffs of 2 seconds equals 10 seconds of puff time. So (seconds) divided by (puffs) equals (average puff time). He provided two sets of numbers. One of the sets came out to 0.08something and the other came out to 0.07something. When I change 1/13 to a decimal it comes out to 0.076something.