Explain the modified the Apdex formula.
Explain the modified the Apdex formula.

This confuses everyone who compares the formula to the one on Wikipedia.
Make the difference explicit, and in the process remind how the buckets
work.

open-falcon/open-falcon.github.io,chosenken/docs,pdbogen/docs,pdbogen/docs,prometheus/docs,open-falcon/open-falcon.github.io,du2016/prometheus-docs,vic3lord/docs,tcolgate/docs,vic3lord/docs,du2016/prometheus-docs,prometheus/docs,du2016/prometheus-docs,ddfreyne/prometheus-docs,tcolgate/docs,prometheus/docs,tcolgate/docs,open-falcon/open-falcon.github.io,vic3lord/docs,chosenken/docs,ddfreyne/prometheus-docs,chosenken/docs,ddfreyne/prometheus-docs,chosenken/docs,Cepave/openfalcon.io,ddfreyne/prometheus-docs,Cepave/openfalcon.io,pdbogen/docs,Cepave/openfalcon.io