Static Mesh has UVs and lightmap, but UE4 gives 3 UV Channels?

as the title says, the UV Channel 0 and UV Channel 1 are fine and just like the UVs in Blender, but UV Channel 2 is something else entirely (it was from older version of the mesh and the fbx file but now deleted)… So?

By default when you import it will generate new lightmap UV’s on a new channel, make sure to uncheck that option when you import.