我英语不好，看F7教材中看到这样一道题, 是一道改错题(bpp版，p49)，

the accounts receivable control account figure,which is used in the list of account balances,does not agree with the total of the sales ledger.A contra of $5000 has been entered correctly in the individual ledger accounts but has been entered on the wrong side of both control accounts.

给出的答案是

D:Trade accounts payable  10000

   C:Trade accounts receivable 10000

我读这段话的意思是：应收账款总账账户与明细帐的加总数不符，有5000记在了正确的科目但却记反了两个账户的方向。如果按这个意思理解，似乎得不出以上的答案，我想一定是这段话里有一些词理解的不对，请高手指点，谢谢！

contra是冲销的意思，就是说原先冲销的时候做错了

应该是做：

 D: Trade accounts payable  5000

    C:Trade accounts receivable 5000

但却做成了

 D:  Trade accounts receivable 5000

   C:Trade accounts payable  5000

那么就要先把做错的原分录冲销

 D: Trade accounts payable  5000

    C:Trade accounts receivable 5000

再重新做新的冲销分录   

D: Trade accounts payable  5000

    C:Trade accounts receivable 5000