From the diagram attached, we see that they went 1000 ft below the sea level.
Now an altimeter is used to measure altitude depth of an object relative to a fixed level which in this case the fixed level is the top of sea. Since the depth in this case is below sea level, it will be negative.
Aleena expands 2xx+3-5(x-2) as 2x²+3-5x-10. She is mistaken because the sign before 10 should be +10 instead of -10. Hence, the correct expanded form is 2x²+3-5x+10. Hence, this is the required solution.