Like everything else with UP, it's pure numbers manipulation.
They are being "stored dead" in consists on trains, and when a unit fails enroute they put the "stored dead" unit online and then place the failing unit in "stored dead" status thus maintaining their required goal numbers of "stored dead" units....
With the heavier trains, lack of power available, and near zero maintenance we ARE seeing more units fail enroute, I'm talking blown motors...so before too long they'll have plenty of real deal dead stuff to store.