What advantages does the forecasted financial statement method have over the AFN equation for forecasting financial requirements?

What advantages does the forecasted financial statement method
have over the AFN equation for forecasting financial requirements?
Using the AFN equation, we forecasted that Allied would need $114
million of external funds, while the fourth-pass (final) AFN forecast
based on financial statements was $112.5 million. However, the AFN
forecast under the modified statement approach was negative. What
caused the huge change in AFN?