Hi,
In case anyone else is scratching their head, thinking they've gone mad or cannot understand rudimentary mathematics, there is currently a display bug in the simulator for two devices - Fenix E and Fenix 8 43mm.
I have created a bug report here: Device simulator wrongly positions screen for fēnix 8 43mm and fēnix E - Connect IQ Bug Reports - Connect IQ - Garmin Forums
No biggie as there are plenty of other 416x416 devices you can test on in the simulator, but just in case (like me) you saw the display bug and instantly assumed you'd messed up then spent time trying to debug stuff that isn't broken...
Anyway, enjoy your day 
Vindicated of Dublin