They've done it before (2015 to 2016), and remember it is actually only about 9% above 2016, so I think it is potentially a bit conservative.
They have had to estimate the impact a result of lower occupancy levels due, in part, to the decommissioning of sites for redevelopment and a reduction in the stock of Units available for resale. If development or decomissioning was faster than expected, or demand higher than expected, there is a chance they could beat forecasts. The opposite is also true of course.
84 cents would make Oceania very attractive in my view, if this were to be the case.