#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// The LCD display you have is I2C with 4 wires
// Connect Vcc, ev as normal - SCL and SDA as per device - on UNO:
// SCL - pin A5
// SDA - pin A4

LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to ex27 for a 16 chars and 2 line display

// setup a variasble and set to 10 to start
int mynumber = 10;

void setup()
{

// initialize the LCD
 lcd.init();

// Turn on backlight 
lcd.backlight();

// Print top line
 lcd.setCursor(0,0); 
lcd.print("Counting down...");

}
void loop()
{

// Print top line
 lcd.setCursor(0,1);
lcd.print(mynumber);

// Cover any left over characters
lcd.print("    ");

delay(1000);

//decrement mynmber
mynumber--;

// I could also have used my + mynumber - 1

}