A big number at the end of a projection makes it tempting to credit all the growth to the investment. To see where the money comes from, separate the starting amount, your contributions and the return.
An example with numbers
You start with $2,000 and add $150 a month for five years. You will have put in $11,000 in total. If a scenario shows a final balance of $12,400, the $1,400 difference is the projected return.
Try it with your numbers
Enter those amounts and compare two return assumptions. Notice which part of the result stays the same when you set the return to zero.
Example figures for learning purposes. They are not a recommendation and do not replace professional advice.