Electrical – How to calibrate PT100 with Arduino

Im trying to use my PT100 with an Arduino-based PLC from Industrial Shields, which is basically an Arduino Mega encased in a plastic container. Im using a 250Ω resistor, actually 237Ω resistor between Analog and Ground.
The pt100 range is -200 to 600C & the transmitter according to NFC scanner is -200 to 600C as well.

Here is my code:

int sensorValue = 0;
int temperature = 0;
int ReceivedByte = 0;
float f1 = 0;
float t1 = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("hi...");
  //analogReference(INTERNAL2V56);
}

void loop() {
  delay(1000);
  sensorValue = analogRead(A2);
  Serial.println(sensorValue);
  /**
   current voltage(250 Ohm) ADC Temperature
 -----------------------------------------------------
 4 mA 1 V 205 -50 C
 20 mA 5 V 1023 +150 C
   * 
   */
  //original 5V adc values from weber 194,971
  //SO-weber new values 10 bit ADC 97,485
  //204-1023 for 10V ADC with 2x237Ω
  // map the signals (using 194-971 for 5V and 97-485 for 10V)
  // to get decimal values, because map() doesn't work with floats)
  // V = 0.004A x 237Ω = 0.948V => 1024 x (0.948/5) = 194.5 lower bound
  // V = 0.020A x 237Ω = 4.74V => 1024 x (4.74/5) = 970.7 upper bound
  temperature=map(sensorValue,194,971,-200,600);
  f1 = temperature; // Float conversion
  Serial.print(f1);
  Serial.print("\n");
}

I was also told to try 500Ω (237×2=474Ω) with the full values of 10V (due to the datasheets from IS) instead of 5V but that doesn't pan out either as can seen in the results table below. I tried:

A- 5V full value & 237Ω
B- 10V full value& 237Ω
C- 10V full value& 474Ω

I've tried all the wiring options available with my 3 wire pt100.

So Im wondering about 2 possibilities:
1. Which is the correct wiring configuration, because I want to eliminate that variable.

2. Could it be Industrial Shields datasheets are incorrect? I just checked the actual plc box and it reads "Analog 0-10VDC" so I dont think IS datasheet is incorrect.

UPDATING RESULTS:
What I dont like about room temp measurements is that its obviously off because it is no 10C in my office, its 22C with a thermometer. But more importantly that it is wildly erratic, ranging from 0C to 12C at times. An average of 100 measurements yields about 10C. I just stuck it in a cup of coffee and the digital thermometer reads 61C and the 100-average of the pt100 reads 58C, so thats encouraging. But individual readings range as low as 47C so its still erratic.

Here are the results:

Thanks