What is the meaning of this sign?

1. Correct answer: Steep downhill slope about 2,500 meters ahead.
2. In 2,500 meters a steep uphill climb begins.
3. Steep downhill slope for 2,500 meters begins here.
4. The end of a 2,500-meters downhill slope section.

WhyHere the plate shows that the steep descent begins about 2,500 meters ahead. If the descent starts right away, the plate says so differently.