Answer:
When the numbers are giving us magnitude relative to a fixed point.
Explanation:
In cases where the sign of the numbers are just telling us magnitude.
For instance the sign of the slope tells whether the line moves forward or backward.
But when we are considering the steepness of the line, it makes sense if we compare the absolute value of the numbers.
The greater the absolute value, the greater the steepness.
Also distance below or above sea level.