I think what Raiboe is saying is that with the autothrottle engaged and lvl change is used in descet after retard has been anuctionated the fma then displays arm. It allows the throttles to be moved manually to any postion and will not be moved by the autothrottle until the speed is so many knots above the commanded speed. With this in mind with the autothrottle in arm mode it gives you low speed protection should the speed decay into the red band (ng series).