Ann: Media Release 30 June 2021 Results, page-7

Just had a quick look at the Receivables numbers across the last 5 years:



I would think that the 2020 year is the anomaly rather than there being too much concern about 2021.
I'm starting to get a bit nerdy here but the average debtor days or the number of days before revenue debt becomes cash can be reflected roughly via the following table



In this table the average Debt is simply the start and end debt divided by 2 to achieve the average debt for a year which is then divided by the revenue for the same year and multiplied by 250 (the number of working days in a year) to get the outstanding period for the debt.

All up I doubt there's anything to worry about here.