A few points,
1) Agree with above post, 0.3% is sweet FA in the grand sceme of things.
2) As mentioned above they make it clear at the selection that you're not against others. If you make the pass rate you move on. If you don't, you don't! There is no grading system as such.
3) There were about 3 or 4 28+ yr olds on my selection day.
4) the selection is actually quite fun.
A3