Dynamic info inside gui

Hi, found awesome ideas of guis and want to realize similar to that screenshot, i understood briefly how to apply gui ( negative space font if correct ) but found this gui and got interested, how can we show dynamic info inside gui so it looks like a part of it, surely we can draw million of variants and cap money to 999,999), i wonder if we can show string as well
Using Paper/Folia 1.21.10 for it