Wiley Mock Question 5 Duration Gap

Wiley Mock Question 5 Duration Gap talk about how the duration of assets decreases while the duration of liabilities increases. Then the duration gap is defined as:

D_A- D_L

Then they argue that the duration gap therefore decreases.

But I thought the duration gap was simply the difference between duration of assets and liabilities, that is here the gap should get larger (in absolute terms). Are we not using the term in absolute terms?

Duration Gap = Duration of Assets - Duration of Liabilities

In the question, they say D of A decreases and D of L increases

So, the gap (difference) between the two decreases

Duration gap is not in absolute value.