@Jeff Hyatt, I was able to find an S3 report that someone created in a sandbox, but looks like the columns are what you're probably already using (Resource ID, Account Name, Cost (Total), GiB Hours, Requests, and Data Transfer (GiB)). Will ask internally.
In terms of things not aligning to AWS, I think you're right - probably billing mechanics. To drill further, would need to know if there are any discounts applied, what numbers are you seeing in AWS vs what CLDY is showing, are the date ranges the same on both sides, etc.?
#Cloudability