I don’t think such a letter exists but I could be wrong. The numbers I always heard from the Borg was how many new building projects that were supposed to be going on and why they need our money. As for hall closer and sales I think they have only stated that these moves were to help with space and better use of it. No numbers being mentioned for they dont want the average JW to start and put two and two together.
There was some accounting videos that mentioned some numbers saying they had a certain vacancy rate etc maybe that’s where any numbers may have been discussed.