From the reports exported from Amazon S3, the value is in "TimedStorage-BytesHrs" It's not very useful if you're doing cost analysis.
Below is the formula to convert it to a usable GB-Months format.
TimedStorage-BytesHrs * 30 * (1 GB/ 1,073,741,824) * (1 Month/744) = GB-Months.
GB-Months x .03 = Total Cost per month.
