Retirement Planner - Cash Flow v. Investment Withdrawal

Hello! I am confused about the use of the Investment Withdrawal section. If your Cash Flow sheet has all of your income and expenses, then what is the purpose of the Investment Withdrawal section of the retirement planner sheet? The investment math considers these separate, and adds them. Is the Investment Withdrawal section just a way to capture some extra spend you may use in retirement? If so, what is a typical value here? Understanding this drastically changes the future value of your plan…

Cashflow is more about netting transaction data whereas investment withdrawal is about making changes to account balances through transfers.