So you're saying if I flip a coin 100 times it might come up heads every time?
The law of averages says it should be around 50/50. Sure it might be 51/49 due to the wieght factor on 1 side of the coin versus the other, but over a full session of coin flipping it will even out.
Similarly, over a full football season, the 4th down conversions will even out. Not to get all high and mighty, but this is called regressing to the mean. I know that is technical talk but what it means is that the Bills will probably not stop too many more 4th downs this year.