Using an HP Up will give your Clefable 10 HP EVs which can be translated to 2 HP points (10 / 4) and the effect will remain on your Clefable whether you fight AI trainers or actual people.If I use an HP Up on my Clefable, sure his HP will raise but it will have an effect in battle with real persons? Does it gonna to raise his HP or it will have no effect?
(Sorry if I am not really good in english)