u8glib delete caracter

i want to delete a caracter but i dont find the instruction of that ! exemple when i want to write a counter the caracter will be ecrased ! if he count 0 , 1 the 1 writen ecrased the 0 so you can not read the both

int i = 0 ;
void draw(void) {
  // graphic commands to redraw the complete screen should be placed here  
  u8g.setFont(u8g_font_unifont);
  u8g.setPrintPos(0, 20);
  u8g.print(i);
 delay(500);
}
void loop(void) {
  // picture loop
  u8g.firstPage();  
  do {
    draw();
      u8g.setFont(u8g_font_unifont);

     u8g.setPrintPos(0, 20);
  u8g.print("      ");
    i=i+1;
    delay(1000);
  } while( u8g.nextPage() );
  
  // rebuild the picture after some delay
  delay(500);
}

Do not change i in the inner loop. Instead do this:

int i = 0 ;
void draw(void) {
  // graphic commands to redraw the complete screen should be placed here  
  u8g.setFont(u8g_font_unifont);
  u8g.setPrintPos(0, 20);
  u8g.print(i);
 delay(500);
}
void loop(void) {
  // picture loop
  u8g.firstPage();  
  do {
    draw();
  } while( u8g.nextPage() );

    i=i+1;
  
  // rebuild the picture after some delay
  delay(500);
}

For details, see here: https://code.google.com/p/u8glib/wiki/tpictureloop

Oliver