This is a link to the toilet web page for anyone following.
Ebler.
The first thing I would do would be to assemble the tank onto the bowl and then install the rubber adapter onto the toilet to measure the difference between the adapter and the back of the toilet tank which is the closest the toilet can be to the drywall surface (you want to have some space between the wall and the tank to prevent moisture/mildew) . This will also allow you to measure the height above your
Finished Floor that the drain needs to protrude from the wall. You can be slightly higher but in no case any lower than that measurement. You need to know what height exactly your finished floor will be now.
From the spec sheet provided on the above link, the outlet is 6.5" above the
finished floor. That is the height that the drain from the wall needs to be set at. You will need to find an adapter like the black one you have but shorter and with a stainless steel jacket (mission band) that is the same size as the white adapter with rubber seal and the drain pipe in the wall. Use a 45 or 22deg elbow to raise the drain to the height needed
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PS: I'm logging off. Will be out of the country for the next 2weeks.