Problem related to Arduino ip address

Question

Can anyone explain to me why my output ip is: 15.16.17.18?

I configured my addresses as follows:

Arduino :
gateway 192.168.1.1
ipaddress 192.168.1.8
subnet 255.255.255.0

My local network:
gateway 192.168.1.1

ipaddress 192.168.1.3

subnet 255.255.255.0

Then when I print it, it shows 15.16.17.18

Arduino code:

#include <SPI.h>
#include <Ethernet.h>

// network configuration. dns server, gateway and subnet are optional.

// the media access control (ethernet hardware) address for the shield:
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };  

// the dns server ip
IPAddress dnServer(192, 168, 1, 1);
// the router's gateway address:
IPAddress gateway(192, 168, 1, 1);
// the subnet:
IPAddress subnet(255, 255, 255, 0);

//the IP address is dependent on your network
IPAddress ip(192, 168, 1, 8);

void setup() {
  Serial.begin(9600);

  // initialize the ethernet device
  Ethernet.begin(mac, ip, dnServer, gateway, subnet);
  //print out the IP address
  Serial.print("IP = ");
  Serial.println(Ethernet.localIP());
}

void loop() {
}

My output is:

IP = 15.16.17.18

Please help, thank you.