function _withdrawTo(uint _deposit, uint _withdrawn, uint _blockTimestamp, uint _total) constant returns (uint) {
		uint256 fraction = availableForWithdrawalAt(_blockTimestamp);

		
		uint256 withdrawable = ((_deposit * fraction * _total) / totalfv) / precision;

		
		if (withdrawable > _withdrawn) {
			return withdrawable - _withdrawn;
		}
		return 0;
	}