Arduino Serial Monitor printing setup output twice

Question

While working on a project, I found out that the Arduino Serial Monitor was printing the output of the setup() function twice.

So, in order to test what was actually happening, I tried it out with the following sample code:

const uint16_t MOD = 150;
const uint16_t val = 53314;
const uint16_t m = 30;
static uint16_t count = 0;

void setup() {
  uint16_t A[m][m];
  
  Serial.begin(9600);

  for (int i=0; i<m; i++) {
    for (int j=0; j<m; j++) {
      A[i][j] = val % MOD;
    }
  }

  Serial.println("DONE");
  Serial.println(A[0][0]);
  count++;
  Serial.println(count);
}

void loop() {}

And found out that every time I upload the code to Arduino it prints the setup() output twice.

Can someone please provide an explanation as to why this is occurring?

The configuration of the system that I am using to upload the code:

And, I am using an Arduino UNO board.

Answer 1

Even a delay of 200ms worked for me. Any Lower and I have double prints