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#1
Some confusion here. The figures you have added up are NOT the space used on the disk, they are the rate (in MB per second) that data is being read or written to the disk. The 100% means the disk is working at its maximum access rate.
23MB per second sounds about right for sequential read/write to a single file on an HDD, but you have multiple processes accessing multiple files. Seek time is reducing the data throughput to a lower rate.
Why not resume the discussion you started here: In Task Manager, Disk full doesn't match display ? (Starting with the answer Bree already gave you)