The Usage Reports generated by your VPSA Object Store provide an average storage usage over a given timespan. By default this is monthly, but a custom timeframe can be selected as well.
Every VPSA Object Store logs the account usage in a ~30 minute interval which it later uses to calculate a sum of the capacity used during a given time period in a GB/month format.
The VPSA Object Store will keep up to 3 months of this metering data.
Some additional information can be found on our VPSA Object Store user guides page.