Project Timeline
August-September: Deploy/sell all hashpower arriving in July and early August.
September-November: Deploy/sell the hashpower ordered at early July.
November-December: Experimental products of 2nd-gen chips and modular large-scale deployment solutions.
I believe this refers to bolded part. Now it has been specified to be done in october.
The sales have been happening all through that period, the 500TH info is merely saying that supply will be increasing. Note that blades are, and have been, available and selling.