No worries RVDT,
Ok, for explanation purposes, you enter autorotation and once stabilised, lets say at 90kts and 100%Nr, you twist off the throttles to the red button stop. This causes the N2s to run down to 60%.
At 100' you start your flare and have a nice little cushioned run on, slowly lowering the collective to slow yourself down. With the collective fully down the Nr decays to 60% whereupon the free wheels re-engage and keeps driving the gearbox at 60% until you do something to affect it.
Hope that explains it along with the help of a picture, with the triple tachometer (Nr Needle, with #1 N2 & #2 N2 needles behind), top right.
