[savings and investments concept]

Please explain this to me/ draw whats happening in this scenario:

A 20 year old started saving and investing $300 per month and had a 7% growth rate, by the time they would retire they would have over $1,000,000 saved. This assumes that they plan to retire at age 66 and are able to invest every month at the $300 per month rate. The total amount the client would save and invest just over $165,000 and the remainder is due to the compounding interest associated with the investment earnings.