How to have seat numbering vertical instead of horizontal?

[xithalius]

How can i turn:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

Into:
1 5 9 13
2 6 10 14
3 7 11 15
4 8 12 16

[mateuszmarkowski]

You will have to override the default implementation of getLabel. GetLabel is responsible for generating labels.

[sugoireed]

You will have to override the default implementation of getLabel. GetLabel is responsible for generating labels.

I've figured out how to override. Any pointers on how to get the actual numbers?