Can someone explain what is going on?Production of concentrate...

Can someone explain what is going on?
Production of concentrate for the quarter at an all time high. But cash receipts totalled $772k. Last quarter was less production but receipts of $2.281m. So x3 revenue on less production.

The reason given was:
"as a result of timing differences between invoicing and actual shipment of concentrate around the calendar year end"

Does anyone know exactly what this means?

This explanation doesn't exactly say much.
 Q4/22 and Q1/23 customer receipts in aggregate $2.401 million
 Q2/23 and Q3/23 customer receipts in aggregate $3.053 million (representing a +27% increase vs.
Q4/22 and Q1/23)

apart from they had less revenue this latest quarter than they did in the last 6 quarters.....

Q1 2023- Receipts $0.772m -Jan/Feb/Mar 2023 (Q3/23 in the above)
Q4 2022- Receipts $2.281m -Oct/Nov/Dec 2022 (Q2/23 in the above)
Q3 2022- Receipts $1.425m -July/Aug/Sept 2022 (Q1/23 in the above)
Q2 2022- Receipts $0.976m -Apr/May/June 2022 (Q4/22 in the above)
Q1 2022- Receipts $0.822m -Jan/Feb/Mar 2022
Q4 2021- Receipts $1.209m -Oct/Nov/Dec 2021
Q3 2021- Receipts $1.802m -Jul/Aug/Sep 2021
Q2 2021- Receipts $0.615m -Apr/May/June 2021
Q1 2021- Receipts $1.035m -Jan/Feb/Mar 2021

So based on the quarterlies this March quarter was worse than that of 2022 and 2021........ WHY?

Not to mention a highlight from the quarter ended 20 September 2022 was
"Debottlenecking of slurry pipe and trials of additional crushing capacity ahead of Gravity Plant deliver further improvements."

And a Highlight from this quarter
"Upgrading of slurry pipe connecting crushing plant with gravity plant set to deliver improvements and trials of additional crushing capacity continue to deliver further improvements"