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Increasing the amount of Cylinder would only be virtual and testdisk would give out read errors reading not available physically storage.
You should have a look to get your disk capacity back.
There are tools like hdat2 in case.
But I can't judge your situation because I've no info.

thanks for ...

I have a ST500DM002 hdd but I only see 4 GB !! is a 500 GB !!
I tried to reconstruct testdisk cylinders, sectors etc but I have all the data that testsidk ask me!
You have the possibility to give me any information?
seagate website I found a pdf with the initial characteristics of the cylinder ...