CCleaner wiped free space still recoverable with Recuva

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I wiped the free space on my external 2TB hard drive using CCleaner, but each time Recuva is able to recover the the same 300,000 files that are approximately 5 GB in total size, complete with file names.  They all say "not overwritten" and "excellent".  A random selection to recover successfully recovers them.  The recycle bin is empty.  The drive is split into 2 partitions.  The 1st partition with the problem has existing files on it which is why I used "wipe free space".  The 2nd partition is empty and I used "wipe entire drive" and that one doesn't return any results when searching with recuva except for a few small system files that are created on format.

What is it that I'm doing wrong, or why are the same files still recoverable after using the wipe function?