Losing Free Storage Space ?!

My PB came back from the shop replaced due to the back casing bulge � happily re-united, but single problem � for some reason I lost roughly about 3GB of space.
I only have about 1GB of music file, and under 30MB worth of Apps, 10MB of books, nothing more! , but my 32GB shows that I only have 25.1GB of free space out of 29GB. How can this be? I expect to see something like 27GB.

I cleared all the browsers, security wiped once, OS updated � all possible thing that I could imagine � same !

Can anybody able to address this issue?

I guess there might be something going on under �protected_media� folder...
I wish someone come up with deep clean app to free up storage / RAM !

Backup using Desktop Software and wipe the device.

Check if you have the expected amount of memory then (whatever that would be). Then reload the backup and see what free space you have.

just updating the matter...
I did security wipe - but free storage space shows 26.6GB out of 29.6GB.

This I notice after I RMA my playbook, before I did not pay much attention since I was too excited to own PB and keep loading thing in.

Was it always 26.6 GB of free space for all 32GB model or just mine?

any help?