Many exchanges charge fees to their members for orders that are cancelled or modified, and IBKR charges certain related fees to its customers to help cover these exchange fees. Please note however, that the Modify/Cancel fees listed are not intended to be a direct "pass-through" of exchange fees. The Modify/Cancel fees that IBKR charges to its customers may be higher or lower than the fees that an exchange may impose on IBKR. IBKR may charge Modify/Cancel fees to its customers for orders sent to exchanges that do not impose such fees, or vice versa.
Execution credits are applied against cancel or modify fees in the same product on the same day. Execution credits cannot exceed cancel/modify fees.
Please see the Cancel/Modify Orders and Cancel/Modify Futures/Options Orders sections on Other Fees page of IBKR website. Find also some useful examples.