I had something similar happen to me, they said it was "as I didn't work the whole year and its rated over a year". but I only was @ work for the last quarter of the year!!

I'd be asking for the ratings you had, and justifications as to why that figure matches your performance. I know its hard, but start with keeping the mat leave out of it - it was only what, 2 months into the last financial year, and really, people go on leave for that amount of time often. Start with doing a "review" of your work, and see if their review matches yours. The amount of time you've been working doing a job is unfortunately not a reason for a higher $$$ figure, but the quality of your work is.