Perhaps you have problems with updating the databases, like there: Search results for 'used space reset order:latest' - Storj Community Forum (official)
You may try to recreate these databases:
And restart the node, the stat should be updated. This is for a piecestore backend, though.
However, if you enabled hashstore (the subfolder with hashstore should be greater than blobs), then the numbers going to be updated much less frequently and it’s would be an estimation, not the exact usage.