Compound interest is interest on interest. Very crude example, you put away R100 at 5% for 10 years. Year one you earn 5% on R100 which brings you to R105. Year two you earn 5% on the R105 instead of just the initial R100.
Shares have a similar snowball effect.
As far as I understand EE dividends are not automatically reinvested. It is credited to your account and available for withdrawal or investment. If you want to earn "compound interest" on your dividend portion you will have to reinvest it.