Hello, I'm glad you enjoyed it. Sorry if my answer is wrong.
First, layering the same instrument at the same pitch sounds like a bit increase the volume of one note.
This is because two exactly the same waveform are played with exactly the same timing, so you only hear one sound. It doesn't sound like the volume has doubled either.
If you want to get a loud volume, it is more effective to raise the volume value from ”C" to "F" than layering sounds.
Also, if you want to make it sound like two sounds are playing, it is good to change the insturument and layer it. It is also effective to change the pitch by octave.