By default, the library allows a schedule to run in parallel with a previously triggered execution of the same schedule.

If you don't want such behaviour you can set a specific schedule as non-reentrant:

public class MyRegistry : Registry
{
    Schedule<MyJob>().NonReentrant().ToRunEvery(2).Seconds();
}

Or you can set it to all schedules of the registry at once:

public class MyRegistry : Registry
{
    NonReentrantAsDefault();
    Schedule<MyJob>().ToRunEvery(2).Seconds();
}