Error sensor reading on apps

MIT App Inventor Help
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Suppose to be after the count is the output from Arduino. Please help. Newbie here huhu

Here is the code

#define trigPin 6
#define echoPin 5

void setup() {

Serial.begin (9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);

}
int countgrab=0;
void loop() {

int duration, distance;

digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance = (duration/2) / 29.1;

  if (distance >= 300) {

  countgrab++;
  
     
     if (distance <= -300){
 countgrab++;
  }

}

  Serial.println(countgrab);

delay(200);
}