Limit show CO2 index within 4 character number (max = 9999)

examples/ONE/ONE.ino

@@ -1453,6 +1453,10 @@ static void displayShowDashboard(String err) {
     /** Show CO2 value */
     u8g2.setFont(u8g2_font_t0_22b_tf);
     if (co2Ppm > 0) {
+      int val = 9999;
+      if (co2Ppm < 10000) {
+        val = co2Ppm;
+      }
       sprintf(strBuf, "%d", co2Ppm);
     } else {
       sprintf(strBuf, "%s", "-");