be sure and use coin control
Is there a manual on coin control somewhere?
Here
https://bitcointalk.org/index.php?topic=487814.msg10296134#msg10296134 
Edit:
Use Coin Control and send back exactly 2015 zeitcoins to MgUFJ2AJvhaWsW4kkfwoDuzy2pZSQLJB63 , from the 2025 that was sent to you.
(Only send from the block of 2025 sent to you, sending from another block , can cause the entire block amount to be subtracted from your total by the block explorer stats.)