This refers to your PAYS subscription expiry, which is automatically renewed when you receive updates, unless you stop your subscription with us. The PAYS subscription license is valid for 3 months, and you will get this message displayed in your system less than 30 days to expiry.
Unfortunately we're not allowed to renew the PAYS subscription before after start of the month which it is due to expire.
When updating less than <30 days to expiry, and then load permits and charts in ECDIS, the subscription license will also be updated automatically.