Based on the fact we count the 6,000 ST Holders regardless of whether they turn up, I guess it would be tickets sold.
I only say it based on comparable crowds such as Coventry City, Leicester City, Leeds United and many others who have brought 4,000 upwards. In my opinion, it looked right. A fantastic turnout regardless and just a shame we could not manage a thousand or so more at our end, seeing as we had 10,500 there.