I made a mistake when calculating amount of refund request during a dispute,can it be corrected?

[Robert667]

   I do not know how I made the calculation error.
 I ordered a item with additional accessories to get refund request amount I subtracting the good items from the cost of the main item that was defective and made a significant mistake.

 
 This is for clarity not the actual amounts but for example the item that was defective was 500.00 for example and I put amount of refund request as 250.00.
  Can this be changed after the dispute or claim has been started?

 If it can’t be edited I’m already at a significant loss and am better off closing the case because the refund amount is completely wrong and will actually cause more loss.

[Robert667]

 I wanted to clarify a bit more.

I bought an item for let’s say 500.00 and bought 5 accessories for it that added up to 50.00.

 The item that was 500.00 was defective and what I requested a refund amount for but I entered a wrong amount and put 250.00 for example.

This is my first dispute and I can not find any way to correct it.

 If I cancel the dispute I’m assuming it can not be reopened.

    Thanks