Immortal card stack size glitch?

I currently have 5x immortal card 2 dropped . 2 gambled and one purchased from another player. Why does my stack size say 5 of 10 instead of 5 of 9. also tried to post on trade site and they wont show up.Item Class: Divination CardsRarity: Divination CardThe Immortal--------Stack Size: 5/10--------House of Mirrors--------"Greetings! Just because you think I'm greedy doesn't mean I'm not willing to share. You'll just have to kill me first."-Grandmaster Dy'Ness--------Shift click to unstack.

The stack size of Immortal is 10. The stack size of House of Mirrors is 9.

If you get 5 more Immortal cards to turn into a House of Mirrors, then it will become 1 of 9.