How can voided 1 line in a check has more than 2 lines?

Hello @chidao ,
Maybe you can try out Reverse Application option:
I have created 2 bills for 2 POs for the same vendor:
 

Now assuming i would like to void the bill no. 000170, i would click on Reverse Application button. This would remove the respective bill from the check, but this would also require to add another bill in order to nullify the Unapplied Balance.

 

From here, we would could other bill, in order to Nullify the Unapplied balance. So here, I would now apply other bill (bill no. 000172). Upon adding the system would automatically deduct the amount from the total bill amount, and hence, apply the check to the particular bill.

 

Upon Saving and Releasing the Check, the below adjustments are made in the system:

 

Also, the system updates the balance for the bill that was removed (000170) and also for 000172.

 

Hope this helps to you!

Regards.