Supported rule and example

A level-1 card targeting level 21 needs 20 Tomes. With 7 in inventory the shortfall is 13. A level-15 card targeting 21 needs 6; already being level 21 does not create a route to 22 through Tomes.

The calculator rejects a target below the current level and levels above the supported cap. It also rejects fractional or negative inventories. For a card already above 21, use its spare-copy panel in Army.

See Card Tomes, card upgrades and codes for the rule and sourced rewards.