How to bold and make letters full on a 2D WLED led matrix

this is how to do it : segment-grouping = 2
I’ve tried it on:
led matrix ws2812b (32x16)
size screen (32x16)cm
led matrix ws2811 (40x20)
size screen (240x120)cm
esp32
https://www.youtube.com/watch?v=nrm8x73ZCy8

Could you explain a little more about the segment grouping, I’m trying to do this myself and not having any luck. If you could describe in more detail that would be awesome, thanks!