This could happen when you have transactions recorded before the opening balance date.
Let’s take an example where you have entered R1000 as opening balance dated on 01-01-2016. But, you have a transaction recorded for R500 on 25-12-2015. In this case, the opening balance amount would take account of the R500 income and will display the opening balance as R1500.
To rectify this issue, it is advisable to set opening balance to a date before the date on which the transaction was recorded.
Books
Online accounting software
for small businesses.