Using a Sparkfun display for a counter

Projects General Guidance
4

I would get it working in the serial monitor first then get it writing to your particular screen.
Something like this (not at all tested).

int x=300;
int Button=5;

void Setup()
 {
Serial.print(x);
digitalWrite(Button, HIGH);
}
void Loop()
{
 if(digitalRead(Button)==LOW)
{
Countdown();
}

}

void Countdown()
{

for (int i=300; i <= 0; i--){
      Serial.print(i)
       } 
}