15 magic pen is giving 14 magic pen

15 magic pen from both runes and items is only giving 14 magic penetration - this is a significant bug as it will prevent one doing slightly less damage, and in certain scenarios will result in someone getting away when they should have died.

And it is all 15 magic penetration value (so 15 mpen on runes, and 15 mepn from sorc boots will grant 28 mpen and not 30 pen) long standing bug is that 15 magic penetration runes will be stated as 14 magic penetration, this has never been a problem until recently since before it never effected the in-game penetration but now it is.

EDIT: Okay, so this bug actually only happens when you are running a rune page with 15 magic penetration and for some reason instead of giving 15 magic pen like it should be it is granting 14 magic pen for EVERYTHING that should be giving 15 magic pen including items.