At the loading screen it says that the apprentice stone doubles your magicka and your magicka regenaration but when i activate it,at the active effects section it says that only my magicka regenaration is doubled.Is it a bug or the text at the loading screen is wrong?

The text is wrong, They prob had double mana before the game shipped but then thought it might be overpowered so they changed it and forgot to change the tip text on loading screens.