When you add subscriptions to an existing pack, the initial fees are pro-rated to match the current fee due date for the pack. This prorated fee is included in the sign up transaction.
This is different from what you might be used to with original Ethereum NaaS, where the initial 30 days of fees are included in the NaaS sign up transaction.
Example:
- The existing pack fees are due in 10 days.
- New subscriptions are charged a prorated amount for 10 days of fees, so that they match the existing pack due date.