[GNC] Why is this entry "in and out"

[Mahon Finbar]

Hi,

I have an account for a savings a/c and I want to add the latest 
interest entry. However, when I click the entry title it open with the 
balance, but when I add the interest it fills in the amount as an 
addition and then a subtraction and the balance doesn't change....

Have a the wrong a/c type?In the transfer column it is headed 
Equity:Opening Balances

Thanks, Finbar