A bit of a nitpick: the observed failure rate is quite a bit lower. Each launch involves at least two fuelings, since they do a static fire before every launch (which is when the accident occurred). Every booster also gets tested at their facility in Texas, and there have been a lot of scrubs after fueling, so the average number of fuelings per launch is probably 3 or so. That’s around 150 total fueling events for the Falcon 9, or around 100 if you only count the ones with densifier propellants, making the failure rate so far around 0.6-1%.