No I don't see what you mean. I've reloaded the page and yes I see the zoom window at 300x300 but I also see that these dimensions are specified in the Magic Zoom Plus invocation code:
<a id="ImgStyle" href="/Users/shopv2.e-retailer.co.nz/images/122.jpg" class="MagicZoom MagicThumb" title="Billabong T '"\Shark Attack" rel="thumb-change:mouseover; zoom-position:right; show-title:true; zoom-fade:true; zoom-width:300; zoom-height:300; zoom-distance: 15;">
<img src="/Users/shopv2.e-retailer.co.nz/images/122_300_300.jpg" alt="Billabong T '"\Shark Attack" title="Billabong T '"\Shark Attack"/>
</a>
zoom-width:300; zoom-height:300;So please check your server side code, there is nothing wrong with Magic Zoom Plus here.