Absolute entry index in the resolved surface, e.g., use as a stable row id.
This numeric value (int32) belongs to FInteractionRuntimeResolvedSurfaceEntry under InteractionRuntime.
Designers configure this value in the owning asset or object details panel, while Blueprint logic can read the resolved value at runtime.
UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "InteractionRuntime")
int32 SurfaceIndex = INDEX_NONE;