Custom workout target numbers

why does zwift round target numbers to the nearest 5 in custom workouts. ie if my target for an interval should be 288 the displayed target is 290, but if it was 287, the displayed target is 285? there is a huge 5w difference in this example for only a 1w difference in target numbers.!

Yeah that´s super wierd. Did you also notice that ERG-mode will give you the correct 287w, regardless of the mysterious increase in target watt?

So it´s cosmetic. But unnecessary.