Answer:
<em><u>Index</u></em>
Explanation:
An index is basically an ordered arrangement of all the topics in the book you're reading that is used to enable readers to search for specific things in the book , and is found at the back of the book.
The change from 632 feet to 312 feet because there is a decrease. When there is a decrease it is modeled by a negative number. All the others show positive increase.