$105m of proceeds from aerial pre-sales, page-7

Plough, I'm not certain, but my take is this:

There are two types of "retirement units"...those that earn a yield and those that are used as trading stock.

Usually trading stock is valued at the lower of cost or replacement value which would be (or should be) substantially below asking price...so a 6% reduction to the asking or list price should not conflict with the valuations.
The very great majority of retirement units have been valued to the NPV of the stream of future annuity income....so, the revaluation presumably takes into account a higher stream of income into the future.

I personally think that valuing such assets in this way is the correct one as they are not property assets in the usual sense they are merely assets that generate an income stream.