Electronic – Arduino interface with I2C Pressure Sensor

I have a Honeywell ASDXRRX100PD2A5 I2C Pressure Sensor that I want to read using an Arduino.

Looking at the datasheet, I know that the I2C address is 0x28, and I have had a play with bits of code I've found on the internet, but none of them make any sense. Numbers do increase as I increase the pressure, but not on the scale shown on the datasheet.

Here is a link to said datasheet: http://www.farnell.com/datasheets/1676926.pdf

Here is a datasheet that has information about communicating with Honeywell sensors using I2C: http://sensing.honeywell.com/index.php/ci_id/45841/la_id/1/document/1/re_id/0

Without having much experience with I2C in the past it's hard for my to get my head around it.

Also, here is a picture of my setup:

The code I am using to test it out at the moment is as follows:

#include<Wire.h>
#define sensor 0x28 //Unique bus address 

void setup()
{ 
  Wire.begin();//Wakes up I2C bus 
  Serial.begin(9600);
}

void getdata(byte *a, byte *b)
{
  //Move register pointer back to first register
  //Wire.beginTransmission(sensor);
  //Wire.write(1);
  //Wire.endTransmission();
  Wire.requestFrom(sensor,2);//Sends content of first two registers
  *a = Wire.read(); //first byte recieved stored here
  *b = Wire.read(); //second byte recieved stored here
}

void showdata()
{
  byte aa,bb;
  float pressure =0;
  getdata(&aa,&bb);
  Serial.print("byte 1: ");Serial.println(aa,DEC);
  Serial.print("byte 2 ");Serial.println(bb,DEC);
 delay(1000);

}

void loop()
{
  showdata();
}

I am getting the following results at the following pressures:

0psi    byte1: 31
        byte2: 246

10psi   byte1: 34
        byte2: 102

20psi   byte1: 32
        byte2: 30

30psi   byte1: 39
        byte2: 167

Any help pointing me in the right direction would be much appreciated.