Before the latest update, as you may already know, the plugin was reiterating playlist feeds meaning it would automatically go back to first entry and parse the whole feed again from entry 1 to last entry (in your case 1238). Now, if you have the option checked, it will only look for new videos but only after the end of the playlist is reached. To be more precise, the playlist has to be parsed at least once.
In your case, to check if numbers are updating, look at Next to process column, if those values stay the same ( unless the playlist was parsed once and option to not parse again is on in which case you will probably constantly see 0 – number of videos to import at once ) the update process isn’t running.
About your cron, I think it’s correct but if you’re getting errors it might not be. Again, looking at next to procesws column might help determine if it’s correct or not.