what case does xid wraparound warning messages like example emit?

Hi all,

I have a question about xid wraparound.
The document below say that warning occurs when transactionId which I can use
is reduced to less than 11,000,000.

https://www.postgresql.org/docs/11/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND
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If for some reason autovacuum fails to clear old XIDs from a table, the system will begin to emit warning messages like this when the database's oldest XIDs reach ten million transactions from the wraparound point:

WARNING: database "mydb" must be vacuumed within 177009986 transactions
HINT: To avoid a database shutdown, execute a database-wide VACUUM in "mydb".
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But example message of document wrote "within 177009986 transactions".
What case do I can show transaction over 11,000,000 ?

Best regards,

--
Takuma Hoshiai <hoshiai(at)sraoss(dot)co(dot)jp>