hi! My king is very old and will soon retire, but I'd like to train up the heir I've chosen for the stat boost and I was wondering- if I king the heir as an adolescent with a full training bar, will he get the boost on being kinged? or does he have to be an adult for it to activate and get those extra stats before I king him?

I need to know because I only have a couple days left and may need to use an item to age up my heir if he needs to be an adult for the training boost

Thanks!