There are two ways to override a commission on a specific transaction.
You can go into Settings > Permissions > Turn on the permission labeled 'Allow override of commission plan in a transaction?'.
Next go into the transaction you want to override and scroll to the bottom where the agents are assigned and you'll see an Override Commission Plan option, check the box.
Next enter the percentage you want to use for this agent's split.
Save the transaction and when you create the disbursement the override commission amount will be used for the agent's split.
You can go to Settings> Commission Plans> Add Plan
Create a flat fee commission plan for the split amount you want to use for this deal.
Name the plan
Choose type of plan> Flat Fee
For example, if the agent's commission is $6550 on a $10,000 commission, create a flat fee plan with the agent's % as 65.5.
Save the plan
Go back to the transaction that you need to override the split, go to the bottom of the transaction info page
Select the drop down for the commission plan for this agent and select the new plan created to override the split on this transaction
Then click Save
Re-create the disbursement.
You can use this override commission anytime you need to do this by just changing the agent % for that specific transaction, saving the plan, then editing the transaction and selecting the override commission plan for that deal.