how can i use multiple font size?

[PaekHyun]

I want to use multiple fonts size. What should I do?
If I use the code below, it doesn't work properly.

  display.setFullWindow();
  display.firstPage();
  do
  {
    
    display.fillScreen(GxEPD_WHITE);    
    display.setFont(&BASTION_60pt7b);
    display.setTextColor(GxEPD_BLACK);
    display.setCursor(today_x, today_y);    
    display.print(today);
    
    display.setFont(&BASTION_70pt7b);
    display.setTextColor(GxEPD_RED);  
    display.setCursor(ddaycount_x, ddaycount_y);
    display.print(ddaycount);

  }
  while (display.nextPage()); 

[G6EJD]

Have you included the fonts? If not it will never work.

[ZinggJM]

Maybe one or both of your font files is not in the format Adafruit_GFX expects.
Impossible to know, with the little information you provide.