Once the refunded part of the bank transaction is imported into Easy Cashflow, you categorise it to the same expense category used for the outgoing part of the transfer. This will create the income document (incoming) for it while the original was the expense document (outgoing).
So when you create an expense document/categorise a transaction, that is classed as a debit to that category. When you create an income document/categorise a transaction, that is classed as a credit to that category.