As others have pointed out, there is no direct way to do that in the scheduler.
If the 7 minute interval is vital, then you would have to have some sort of indication for your code to know when the scheduled job was last started - so basically a db field like last_run_at. Then run the scheduler every minute and check if it's been 7 minutes or more.
But what is the use case? There are possibly other and better ways to achieve what you're trying to achieve. :-)
You can run your command every minute, and just check the elapsed time since last execution. If it's less than 7 minutes, you skip. If it's more, you run it.
$lastSynced = Cache::get('last_synced_at');
if ($lastSynced && $lastSynced->diffInMinutes() < 7) {
// Skip... It's not time yet.
return;
}
Cache::put('last_synced_at', now());
// Your code...