How this is calculated
The initial amount grows using A = P × (1 + r/n)n×t, where P is the principal, r is the annual rate, n is the compounding frequency per year, and t is the time in years. Monthly contributions are calculated separately as a future value of annuity, using a monthly rate of r/12 compounded each month they're added, then added to the principal's growth. This mirrors how compounding is explained in most finance textbooks: the earlier you start and the more frequently interest compounds, the more of your final balance comes from interest rather than your own contributions.