gerechnet auf
1.Insgesamt entspricht die Häufigkeit der Konusbrüche, gerechnet auf die 300 Patienten, die insgesamt einen Titankonusadapter erhalten haben, 3%.
it is very complicated, can not understand totally

Altogether, the frequency of "Konus" fractions (whatever that is in that context) is 3%. That was calculated taking into account the 300 patients in total who received a titan "Konus" adapter.

So "gerechnet auf" here means "with respect to the following total number of samples".