Question regarding the ACS758 Current Sensor

So I bought this sensor to measure DC current using my 5v Trinket Pro. I followed the wiring setup and code samples from the website. Everything seems to be working fine once connected, but I'm wondering why is it that once I disconnect the lines from the IN and OUT connections, I still would get a reading? My understanding is that I should be getting a value of 0A once I disconnect them. Am I doing something wrong? 

NOTE: I'm still a beginner, so please bear with me.

Attaching the images of my setup:

Below is the code i used for the Trinket

 

Code: Select all// include the library code:
#include <LiquidCrystal.h>

int RS = 3;
int EN = 4;
int D4 = 9;
int D5 = 10;
int D6 = 11;
int D7 = 12;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(RS, EN, D4, D5, D6, D7);

const int numReadings = 30;
float readings[numReadings];      // the readings from the analog input
int index = 0;                  // the index of the current reading
float total = 0;                  // the running total
float average = 0;                // the average
float currentValue = 0;

// the setup function runs once when you press reset or power the board
void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
    for (int thisReading = 0; thisReading < numReadings; thisReading++)
      readings[thisReading] = 0; 
}

// the loop function runs over and over again forever
void loop() {
    total= total - readings[index];          
    readings[index] = analogRead(0); //Raw data reading

    lcd.setCursor(0, 1);
    lcd.print("Orig: ");
    lcd.print(readings[index]);

    //Data processing:510-raw data from analogRead when the input is 0;
    // 5-5v; the first 0.04-0.04V/A(sensitivity); the second 0.04-offset val;
    readings[index] = (readings[index]-512)*5/1024/0.04-0.04;                    
    total= total + readings[index];       
    index = index + 1;                    
    if (index >= numReadings)              
      index = 0;                           
    average = total/numReadings;   //Smoothing algorithm (http://www.arduino.cc/en/Tutorial/Smoothing)    
    currentValue= average;

    lcd.setCursor(0, 0);
    lcd.print("A0: ");
    lcd.print(currentValue);
    delay(10);
}