Physics help...sort of

I copied the question word for word from the book >.>

Also thanks numbers.

Because Earth’s rotation is gradually slowing, the length of each day increases: The day
at the end of the 1.0 century is 1.0 ms longer than the day at the start of the century. In 20
centuries, what is the total of the daily increases in time (that is, the sum of the gain on the first
day, the gain on the second day)

From the PDF posted. There is that parenthesis which makes it pretty clear what it wants.