What does the UV0 array mean in the Procedural Mesh Component?

What does it represent the UV0 array in this guide

and why the values aren’t between (0,0) and (1,1)?

It’s the uv map, used for textures. Like the points on this image https://shiningflint.files.wordpress.com/2013/05/capture2.jpg

In A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums there is an array like this
TArray UV0;
UV0.Add(FVector2D(0, 0));
UV0.Add(FVector2D(10, 0));
UV0.Add(FVector2D(0, 10));
but uv mapping is supposed to be done with values between 0 and 1 (UE4: Dynamic Texture Coordinates (Animated, Generated UVs) - YouTube), here they appear between 0 and 10.

The code is creating each one of the points of the uvmap (maybe in pixels?), while in the video an already created array of points (the uvmap) is being proyected (scaled or panned) over a texture (where 0,0 is one of the corners of the texture and 0.5,0.5 is the center).

Checked, it wasn’t in pixels. The uv coordinates are indeed between 0 and 1 to match the size of an image (in %), but remember that an uvmap it is not limited to the size of the image. If you put your vertex outside the limits, the image will be “tiled”, it will repeat between 1 and 2, 2 and 3, 3 and 4, etc…