The projection assumes the balances, payments, interest rates, contributions and return rates you entered stay constant unless the calculation itself pays a debt down.
It does not automatically include fees, taxes, inflation, rate changes, market movements, income changes or unexpected costs. Monthly surplus and extra debt payments are directed to debt, payments released by cleared debts move to the next debt, and available money accumulates as savings after debt is gone.
Use it well: Compare a cautious scenario with a more hopeful one. If a decision only works under one optimistic assumption, that is useful information.