How do I know if BleachBit has wiped free space?

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After running BleachBit this is the message I received. Does this mean that it has wiped the area or not?
Hope this isn't a dumb question..... I'm not computer person.

Overwrite free disk space C:\Users\ronda\AppData\Local\Temp 0
Overwrite free disk space Z:\ 0
Disk space recovered: 0
Files deleted: 0
Special operations: 2

Thanks for your help,

Ron

The number zero is normal, even when it works. You know it has wiped free space if it takes a long time. A long time can be from ten minutes to a few hours.

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Andrew, lead developer