By default it will be A K Tan but you can put J A K Tan or John
A K Tan or John Tan. If you intend to put John, you must have a
good reason, eg. your surname is super long aka Pavlyuchenko or s/o
Subramanianman. Sometimes if the name is too common like John, they
will ask you to put John T. (T as in Tan)
Sometimes, those ang mor people will just put their surname, eg
Obama.
See your CSM/RSM anal or not lor.