First of all, the relationship between thrust (Fn) and N1 is unique for each engine model, so the manufacturer should supply the curves from test cell runs with a calibrated thrust stand.
That said, the end points are pretty well defined. By spec, idle thrust will always be about 7% of takeoff, and for your example, this is 22-24% N1. Similarly for TO, 100% Fn will correspond to whatever power management calls for - for the ambient temperature specified for the test.
The 85% point is a bit trickier, although a rule of thumb I've used is the Fn/N1 local derivative in the high power region. I am used to seeing about 2.5% thrust change for each 1.0% N1. Therefore to decrease thrust 15% (i.e. from 100% to 85%) we can expect about a 6% reduction in N1.
Right now I have no way to estimate the 30% approach point, although if you plot the three points above and draw a smooth curve, you won't be far off.
Once again, these are a rule of thumb, but will give you a rough idea of what to expect from the official curves.