If the refunded payment was credit card or debit card funded, the refund amount will be credited back to your credit/debit card account. Click on the "Details" link for that payment to see if this is the case.
If this is not the case, login to your PayPal account, click on the "History" tab and then click on the "All activity (with balance)" option. This will show your running PayPal account balance (in the right hand column) after each transaction and should make it easier for you to understand how you arrived at the current PayPal account balance.
A screen shot is available at the following link...
