It should be the elevation gain.
36,4m / 7,7% = 472,727 m
That’s probably rounded down to 0.4 km.
But there are still some mistakes, not huge, but I am to nerdy to accept 
The climb starts at kilometer 9.1 and ends at kilometer 11.5, making it 2.4 kilometers long. However, some details are inaccurate. For instance, the elevation gain (D+) from 440 m to 560 m is actually 120 m, not 101 m. This discrepancy arises because smaller climbs are combined into one larger climb, ignoring the flat sections in between.
Big thanks to Serge for creating that and @MedTechCD for the translation! I adopted the idea of showing detailed segment information by hovering over the chart and made the necessary corrections. However, the hill detection system works slightly differently, so the segments it generates won’t exactly match the originals. Still, it shows the “correct” values for the segments.
You can take a look, if you search for “Climb Segment”
