These 500,000 FlashV3 tokens will come from the Blockzero Treasury to be distributed to XIO holders and XLP liquidity providers.
The currently ongoing FlashV3 rewards to XIO holders will end on Oct 31st: the 1,000,000 FlashV3 rewarded from July 31 to Oct31 per https://medium.com/bombx/the-path-to-flash-v3-perpetual-liquidity-flashburn-layer-2-7ff61b2c58de
The credits system for November's 500k V3 tokens will work the same in November as it has for the July31-Oct31 period.