What do I do when I get 'No Matches found'

Example: I owe someone £500 but I have to deduct £100 for a loan for which I create a Journal Entry.

Then when I go to do my Bank Matching there is a payment of £400 there but I cannot find a match for it. 

I have already created an Expense for £500 and a Journal entry for £100 deducted for repayment. How do I match the the Journal Entry with the Bank £400 to clear the Bank