Now uou use the stby to extend to 15....the LE should go to full down but still no indication on the TE...
Which is not true for all NGs, some only move the LE slats to full extend when the TE flaps are at 25. Which means one has to know which tab number range has that behavior and the tab number if the plane one is sitting in. If one counts in the time for a standby electrical deployment and the required cooling times, that can take some time.