how to sum times in EXPLAIN for Postgres parallel query
Since parallel_leader_participation is at its default value off, the leader participates in the sequential scan. The I/O times of the worker processes are listed individually, but the I/O time of the leader can only be found by subtracting the workers' times from the total time.
The parallel sequential scan took 65026.980 milliseconds, almost all of the time. The fist number (31764.552) is the startup time, that is the time it took until the first result row was returned. If anything surprises me here, it is that high startup time.