I recognize the importance of fixing this modified bill amount in QuickBooks Online. Let me provide you with possible remedies to resolve this disbalance bill amount.

Before we start, do you have other users that have access to your account? If so, this could be the reason why the audit log tracks the changes made within your QuickBooks Account. You can visit this article for your reference on user roles and access limits.

Moving forward, to fix the disbalance amount, we can exclude the bank transactions and enter the bill manually in Quickbooks. Make sure to match the bill amount to the Melio bill transaction amount.

Here's how to enter the bill:

1. Select + New.
2. Select Bill.
3. From the Vendor ▼ dropdown, select a vendor.
4. From the Terms ▼ dropdown, select the bill's terms. This is when your vendor expects to be paid.
5. Enter the Bill date, Due date, and Bill no. as they're recorded on the bill.
6. Enter the bill details in the Category details section. From the Category dropdown, select the expense account you use to track expense transactions. Then enter a description.
7. Enter the Amount and tax.
8. If you plan to bill a customer for the expense, select the Billable checkbox and enter their name in the Customer field.
9. Once done, select Save and Close.

I'm also including this page for your guide to managing your bills and business expenses: Enter and manage bill and bill payments in QuickBooks Online.

Keep me posted in this thread if you need a guide on creating a report in QuickBooks Online. I'll be here to support you.