7h 57min / 3h 57min !?
7h 57min / 3,95 = 2h 56min

Duration d1 = Duration.standardSeconds(28620);
Duration d2 = Duration.standardSeconds(14220);

System.out.println(d1); // PT28620S
System.out.println(d2); // PT14220S

double result = d1.getMillis()/(double) d2.getMillis();
System.out.println(result); // 2.0126582278481013