Different GMs are in charge of different tickets. Some tickets require the attention of a High GM (example, recoveries) and some only require the attention of a Sub GM (example, general questions). Some tickets require a response back from the player, which can cause a ticket to take longer. If the numbers stayed in order, it would probably take quite a bit longer to go through tickets. Don't forget, don't bump your ticket unless you absolutely have to. Bumping your ticket puts it back to the end of the list!
