The Net Flows column represents the client's total inflows for a given year, minus their total outflows. In other words, did they make more than they spent? Or spend more than they made?
If the Net Flows are positive for a given year, that surplus will be saved and reinvested into the client's taxable investments.
If the Net Flows are negative for a given year, that deficit will be funded by withdrawing from a client's investments in a set order (according to your Withdrawal Sequence setting).
Depending on your chosen Planning Method setting, you may also see a 'Spend Unsaved Cash Flows' column to the left of the Net Flows. See the next FAQ for more.