A ticket is a number. Tokora stores no name; the one key a person can be found by is the mobile number a visitor typed for text alerts, and the forms below answer that visitor by number.
Three fields can identify somebody, though. Every ticket records the IP address it was issued from; staff can type anything into a ticket's note; and if text alerts are on, a visitor may have typed their own mobile number for that ticket. So the rule here is retention: after the window below, all three are cleared on old tickets while the counts, waits and service times stay exactly as they were — your reports do not change.
One visitor, by mobile number
When a visitor who gave their number for text alerts asks what you hold, or to be erased, type the number as they give it. Erasing clears the number, the IP address, the note and the messages on every ticket that carries it, the same fields the window above clears, while the counts and wait times stay. It is refused while one of their tickets is still in the queue.