What is the meaning of "Hineni Meshiv
Rashi: The shade will go back 10 steps that it ascended 1 .
Malbim: I will move the sun. The sign will not be merely via the shade (refer to (Melachim II, 20:9:1:3, 20:10:1:3 and the note there).
Ralbag (Melachim II, 20:10) explains that the sun did not go back, just the shade did. It seems that Rashi disagrees, for he explains that there were 10 extra hours of light that day (refer to 35:8:3:1). (PF)
What is "Tzel ha'Ma'alos"?
Rashi: They are steps arranged in a way that the shade indicates the hour of the day, like a sundial).
What is "Asher Yardah v'Ma'alos Achaz"?
Rashi (from Sanhedrin 96a): The day that Achaz died, the sun descended quickly, 10 hours earlier than usual 1 , so they would not eulogize him. Now they went back, and they were added to the day that Chizkiyah healed.
Radak (Melachim II, 20:11): Ma'alos Achaz are steps (Malbim - a Kli) that Achaz made, on which the shade indicates the hour of the day, like a sundial.
Radak (Melachim II, 20:11, citing Targum Yonasan): On the steps was a rock that [via the shade] indicates the hour of the day.
I.e. there were only two hours of daylight that day. (PF)
