From FCOM DSC 22-20-40-30 Other Computations:
Predictions on ALTERNATES page are based on:
No step can be inserted in an alternate flight plan
- No predictions are displayed for the selected alternate on flight plan pages. However, the flight crew can read ALTN trip fuel and time on the INIT B page before engine start, and estimated time and estimated fuel on board at alternate on the FUEL PRED page after engine start.