Just read the translation guide at faq section

After clicking on the 1st option to train your troops, you will see the following Squad Training Menu:

Option 01. Increase unit HP
Option 02. Increase unit Accuracy
Option 03. Increase unit Evasion
*Option 04a. (At the start of a new chapter there will be a new COMMAND ORDER to learn)
*Option 04b. / [5] (After learning the COMMAND ORDER the 5th Option replaces the 4th spot)

*The last option cycles through the following training types, each time after you train:

Increase unit Anti-Personnel Damage (1st time)
Increase unit Anti-armor Damage (2nd time)
Increase unit Defense (3rd time)
Increase unit Debuff Resistance (4th time)

So after training the Anti-Personnel Damage, the menu option changes to
Anti-armor Damage, then Defense, then Debuff Resistance and finally it
changes back to Anti-Personnel Damage (i.e.: the 5th time you train with that option).

(See [shiroi 0079]'s Translation Guide at the GameFaqs site, for more details)