Each rung is a certificate of deposit with the deposit, the annual percentage yield, and the term you enter. Interest on a rung is deposit times yield times years, using the simple growth the form labels. The ladder total is the sum of the rungs. Rolling a matured rung is a new term you choose, not an automatic bank renewal.
Four equal deposits at four different yields produce four different interest amounts. A higher yield on a longer rung does not change the interest on the shorter rungs. The page adds them. It does not quote a live bank rate.
This is a US certificate-of-deposit ladder, not a Canadian GIC ladder. Early-withdrawal penalties are not calculated. The yields are the ones you type, not a current offer from a bank.