That represents a falling away of 31280.
Some of those 31,280 stopped being a JW due to their own death!
But of course that doesn't explain it all. The majority of those 31,280 stopped for other reasons.
My own thought: The Society has seen their numbers tick up slightly over the past year, and that has coincided with their tougher, more conservative stance. No more university education, no more large gatherings, shun even close family members who are DF, etc.
I suspect that rather than focus on a new date, they will see this modest uptick in growth as "Jah's blessing on their efforts", and will become even more hardline in the future.