Bracket trick (basic question)

Glyphs
1

Hi, im new on glyphs and i try to do the interpolation in cent and dolar, but i cant… I create a copy layer for light and bold masters and put the values of the weight in the bracket so i have:

Light
Bold
Light [56]
Bold [56]

My question is how its work and how i do?, because in cent and dolar light i have 2 components (the letter plus the bar) and in the bold cent and dolar i have 3 components (the letter plus the bar is divide in two parts). Thanks!

2

Must be a single master.

These two Master layers need to be compatible with each other:
Light
Bold

And these Bracket layers need to be compatible with each other:
Light [56]
Bold [56]

Instances above 56 will use the Bracket layers instead of the Master layers.