Sensor data from Arduino to Matlab

int Signal[] = {
  A0,A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14};

Perhaps you need to use long or long long.

    pinMode(Signal[i],INPUT); // set the analog input pins A0~A5 as the inputs
    pinMode(output[i], OUTPUT); // set the digital pins 8,9,10 as the outputs

If you are not going to make the comments correct, get rid of them.

int SenselReading[14];  //set an empty 15 point array

Guess again!

      if (i==14 && j==14)
      {
        
        Serial.println(SenselReading[j],DEC);
        
      }
      else{
        Serial.print(SenselReading[j],DEC);
        Serial.print("\t");
      }

It would be a lot simpler to send the value and a tab, and then send the carriage return and line feed after the two loops end. Yes, it would send one extra tab, but is that really a problem?

      delay(3);

Why?

it always has 225 data points when i view the serial monitor through arduino

You don't seem to understand that serial data delivery is not guaranteed.

Why does the sensor data need to be stored in an array (that is too small) anyway? You never use the array data, except for sending the last element stored. That doesn't need an array.