Why is my first invoice less than $[..]?

When you activate your Wormly account, we treat the amount paid as a deposit for credit against future invoices. We bill in arrears, rather than requiring further prepayment.

Our billing cycle follows the calendar month, with all invoices being raised on the 1st day of each month.

So your first invoice will be less than the value of your monthly subscription, because it will cover a period of less than 30 days.