How would I go about making a health bar ontop of a health bar?

To explain this in detail, how would I make a health bar, that when the top health bar goes fully, the one under it starts going down as if you were losing health, to show you what this would look like. Heres a gif:

I am a mediocre scripter at the moment and I wonder how I would go about this.

Nested frames. Tutorial: How to Make a Health Bar

i suppose you could add two of them? and like use an int value for the first health bar amount, use the default for the second one?

just have a frame under your regular health gui to give it the feeling like it’s going down.

if you wanna get a bit complicated your can tween it and have it move down by checking how much damage the player has taken