Every day we receive the 25 Fastest Growing Volumes report from SM. The problem is, it reports at least one system growing at a rate that can't be right. For example, we have an SCCM server which downloads updates once a month. SM claims that it is growing at over 2GB / day, even though it doesn't download anything on a daily basis.
I'd agree, that shouldn't be right. I'd open a ticket with support. As far as I know, that field should take the average of the change per day (Today's average usage - Yesterday average usage) over the last 30 days and report on that.