Jace, the Perfected Mind seems to make up a random number?!

Jace the PM has a -3 ability which counts Jace's shields, multiplies this by three, then adds that many cards to your graveyard. This works well early on in the game when the numbers are low. But once the numbers get bigger and it has to reach further into your library, the number of cards put into the graveyard doesn't seem to follow any rules.

This makes it an unreliable card, so this needs to be fixed :-)

https://www.youtube.com/watch?v=liCjO4xfWpw&t=1s