I've been playing with the site for several days, and there is definitely some problem with withdrawals, as others have already pointed in this thread.

I requested a withdrawal of 0.1 BTC from my account.
My BTCJAM account was debited 0.0955 BTC
On my address I received 0.095 BTC
The transaction has a 0.0005 BTC network fee, which was obviously deducted from the debited amount, before sending to my address.

Why debit 0.0955 BTC instead of 0.1 BTC in the first place, which was the amount requested?