Hi,
The log file only records the free space on the physical disk. It's not possible to know what other per-account restrictions the host may have placed on disk usage.
If you buy a support deal from http://updraftplus.com/shop/ and send your WP + FTP login details (not here - to contact@updraftplus.com) then you can get professional support. If they find that the problem was due to a bug in UD, then there's a 100% refund guarantee.
David