SCREEN FONT IN COMPUTER-BASED ASSESSMENTS FAR TOO SMALL

I recently sat my very first Computer-Based Assessment with AAT; (I don't mean that I had never done Computer-Based Assessments before but that I had never done any with AAT before). It was only the second exam I have actually ever sat with AAT (the other one was paper-based and years ago and I didn't complete the qualification then). My point is: I found that, after I had got to the assessment venue (which I had never been to before the actual exam) and been sat in front of the screen, that the screen font was far too small for me. Does anyone have any idea what the solution to this is? The Preferences facility in the test screen only seems to be able to alter the colour scheme and not the size. To whom should I speak (possibly for 'reasonable adjustments') and at what point during the period leading up to the exam or at the exam itself? Who is responsible for this - the Training Provider, the Assessment Centre, AAT or who?