This growth is the interest earned on the amount saved; each month you earn interest on the initial amount plus the interest already earned (your money increases over time with very little action required from you).
Let's say I save R1200 on 1 Jan, the bank offers me an interest rate of 6% per annum. A simple interest calculation tells me that I will have R1272 at the end of the year. But come 31 Dec I will actually have R1274.01 🥳🥳
I save R100 per month each month for 12 months, I earn a 6% interest rate, at the end of the period I’ll have R1239.72. That's a difference of R34.29.
Remember that the longer the term the better the interest rate offered by the bank.
ratecompare.co.za Has a great interest rate comparison tool and calculator.