Hello,
Currently you cannot set the default page size for grids in the Web Interface. Approximately in a month we will be releasing a minor update to Adaxes 2013.1 that will contain several enhancements to Adaxes functionality. We will add the possibility to specify the default page size.
By the way, though currently it is impossible to set the default page size, you can always change the page size for any specific search to list the results quicker. To do this, just click the arrow embedded in the Page size field and select the desired number of results on a page.