oh hey bonus stats!!!! Every game needs that, right?? anyway, upon each level up for any character, you'll be prompted with a level up bonus UI, Max HP, Max MP, Attack, Special (Attack value but for magic), Defense, and Speed (Only applies with who the player is controlling, if you wanna run around faster, go ahead, though there's a cap of 50 Speed, once cap is reached, you'll no longer be able to select this bonus.)
Ideally, Bonus stat increases are entirely random and depends on a few factors... (Except for the speed bonus)
1) Character's/Party Member's Level, depending on your level, the higher the level, the bigger the bonuses
2) Character/Party Member, this is also another crucial factor, for example, Martix has tons of Base HP, so you'll likely be able to get a much bigger Max HP bonus than one for Sarge even if they're the same level.
3) Selection Interval, another yet critical key factor is how often you pick a stat value increase, the other 2 which can be beneficial in certain scenarios, this is no exception. Let's say you picked the Attack Bonus 10 times in a row for the same character, upon doing so, the stat bonus increase is very bad... To combat this, if you chose to pick a different stat bonus, it'll not be so bad, but there's another thing to it, if you haven't picked a certain stat bonus for a while, it'll still keep going up and up till you finally select it. Basically, spread out the bonuses you choose for the best outcome of stat bonuses. (Look, got to balance things, ok?)
That's it lol, this'll be interesting! Let me know what you think