Ann: Quarterly Activities Report, page-24

I have a very similar estimate on cash gen of $0.8B, 4m interest, 1.5B FY22 tax, 0.3B Q1 PAYG instalment, 0.2B capex, 0.9B div, that leaves about $0.7B cash balance.
0.3B payg could be altered or deferred into the Q3, which leaves $1b equals to your estimate.

Q3 interim would be interesting, if they go with 50% of 50% payout, that would be $0.25 per share, to me it means the management is comfortable with the current market condition and not really looking to purchase BHP asset. If the div dives, then something we don't know is happening in the background.