What else could that mean?

Yesterday, Spoof sent out an email to everyone on staff at Tartarus about ordering t-shirts, asking for everyone's sizes. And this is how Opie replied:

We took a screenshot so no one could question the authenticity of this conversation.

We ask you, what options are there for t-shirt sizes other than the standard small, medium, large, or extra-large?

This is our theoretical reply to Opie's email: 
     How about Q, 37, Red, Slimey, or Rot?

To make this story even better, this morning Opie took Spoof aside and asked "What does t-shirt sizes mean? Does that mean the size of the shirt?"

Opie talking

Us attempting to respond