First thank you for watching the video so i am sure it is available for others also with private setting :-).
The number of SpawnNormalMacro defines the number of enemies that is spawned with this action.
As I hopefully uploaded this screen from next wave there they use 6 fast enemies, afterwards 6 normal enemies and the next are (last one) are 8 normal enemies.
Problem for me is that I am not able to add the event to the visual editor that seems to tell us that the enemies are fully spawned (e.g. 6 fast ones). So it can be that all OnWaveSpawned are diffent but I do not know this difference only from this blueprint.