There are typically two directions that we can increase a table, in width, or in height. When we consider our table is a list (which are usually represented vertically), a new element inserted anywhere but the bottom of the list will appear to push everything down one index to make room for the new item. This is what the author is referring to. The lowest index is at the top, the highest at the bottom.
In this introductory course don’t get too hung up on semantics. A single dimension list can also be treated as a row. The row grows from left to right so that the leftmost index is the lowest, 0, and the rightmost index is the highest.
Nothing to report so long as you are beginning to understand what the author meant. If you have a suggestion for better wording, then submit it as such, in the other section of the form. However, in the time it takes you to do that, you could be done this unit. How valuable is your time, and will your suggestion be worth it?