1)
What is the meaning of "Halach ha'Tzel Eser Ma'alos"?
1.
Rashi: The verse is abbreviated. The shade had already gone 10 steps (this indicated the hour of the day, like a sundial). Do you want that the shade will stay there for the time to walk 10 hours?
2.
Radak: Which sign do you want - should the shade go ahead 10 steps in one moment
2)
What is the meaning of "Im Yashuv Eser Ma'alos"?
1.
Rashi: Or, do you want that the shade will return 10 steps, as if it is Shacharis?