07:09 May 20, 2011 

Thank you, tulip bubble. There is not much detail, but I believe your first suggestion is correct: the account holder has not spent all of the authorized funds.

I appreciate your point on "unexecuted" vs. "non-executed" too.

04:10 May 20, 2011 

I do not know the relation between the untapped funds in the overdraft account and 借入未実行残高: whether there is the authorized overdraft limit, and the account holder has not spent the authorized funds. Anyways, I would use "unexecuted" for 未実行. Unexecuted means "not carried out or put into effect." If the loan was "non-executed," it implies a certain event kept the lender from executing the loan, which is not likely the case here.