It’s a bit ambiguous but here is what their website says:
“Client disbursements for your shops will automatically be sent through PayPal approximately 30 days after the last day of the month in which your shops were completed. We normally pay on the 20th of the month (or on the following business day). All required shop documentation (business card, receipt, etc.) must be submitted for payment to be processed.
Please keep in mind that it takes PayPal up to 5 business days to process payments once they have been transferred. We ONLY pay via PayPal; no checks are ever issued.“
I have always been paid a few days after the 20th of the month for prior month shops.