If you create a task with low (0) priority on Toodledo and star it, 2Day syncs it as a low priority one (1 bar). However, if you raise its priority by one level, you'll get medium in 2Day.
Apparently, 2Day ignores "starred" status and treats it as just +1 to priority level. In many task managers (Toodledo included) star is just a means to highlight some tasks without meddling with their priorities. It'd be nice to see this behavior in 2Day also.