After entering a schedule such as @hourly or @daily in the "Poll SCM" (SCMTrigger) field the form validation reports when it would have last run and will next run. The times that it reports however appear to be different from the times that the SCM is actually polled. The times for "Build Periodically" (TimerTrigger) appear to be correct.
I have created a job called "TestCron" and that shows different times for Poll SCM and Build Periodically (see screenshot). It appears to me that these should both be the same as they are based on the hash of the item name.