"Assuming FR is 1/7, probability of it missing 23 times in a row = .03"
whatever it is, assuming the FR spot is set at the start of each run, you can only calculate things with this knowledge if you actually get that far every single run. and I assume you didn't do 23 2:20 fails in a row. so calculating it otherwise is assuming the FR spot is set somewhere later in the run, such as just before it appears. but assuming makes calculations often very inaccurate.