Rule 107.17 · Numbers and Symbols
The ticket symbol is {TK}. It represents one ticket counter.
Subrules
A ticket symbol with a number inside it represents a ticket cost. To pay that cost, a player removes that many ticket counters from themselves.
Ask the judge Pro
The life counter has an AI judge that answers your play citing the exact rules. It is part of Gatewatch Pro; the rules, Oracle text and rulings stay free.