If you look at the chart, notice that the batting average (year one to year two) goes from .279 and .281, meaning it went up. To find out how much it went up, simply subtract .279 from .281. This would be represented by this expression:
.281-.279
This expression would then simplify to your answer: 0.002
This means that Aaron's batting average went up by 0.002 in the second year.