I would agree with lomoto - you'll not worry about it after a while. I tend to keep it on the mph readout as it is a more accurate check as you approach speed cameras
As far as the other readouts go on that dial, as far as ai can work out, the DTE is in kms., the average speed is in kph and the fuel consumption is in kilometres per litre. You can convert that by multiplying the figure by 4.5 (litres to gallons) then dividing by 5/8 (kilometres to miles). That gives me a return of around 27 or 28 mpg on Optimax if I don't play too hard! Using ordinary unleaded gives a poorer return, I find.
By the way, mine is also a JDM import with Tiptronic, and I think it is great. There seem to be quite a few out there, judging by some of the posts in recent weeks. If you check websites of importers such as Bristol Import Centre you will see there is a fair turnover of Tiptronics which somebody out there must be driving.
Enjoy the Z - we all do!
Jim