Strange numbers for Passive Perception (Ranger/Cleric)

One of my players plays this: https://ddb.ac/characters/22484769/9foj8f Ranger/Cleric in our campaign and I've just learned that he apparently has a passive perception of 22?

Where does that come from? Or is it a bug I can't quite pinpoint?

The sentinel shield gives advantage on Wisdom (Perception) checks, which translates as a +5 to Passive Perception

If the character has advantage on the check, add 5. For disadvantage, subtract 5.

Thanks a lot - this indeed escaped me - although I have to remember to substract these five points if he is without his shield in hand.