It will depend on the how the subject divides up the papers.
For Modern History we usually only get bundles of 20. Sometimes though we can get larger bundles, depending on the question e.g. some of the more obscure personalities might have only one school but over 30 students (Kita Ikki for instance a couple of years ago) so they kept the lot together as one bundle.
It is possible that a large school group will not only be marked by different markers but even different groups within the same question.
For the personality questions in Modern History there are four tables each marking the same questions (at least for the first few days and then we break up into smaller personalities and one or two tables stick with the Russians and the other two tables finish the Germans). It is therefore possible for a large group to be marked at three different tables with each bundle having only 20 scripts.
When we get the bundles they are in numerical order as that is the order down the marking page, which means that the order you sit in the exam room is the order that we get them given to us.