I completed the Prepare for Your Salesforce Administrator Credential course, after the instructor class was not asked to pay, and received a voucher — is this expected or is there any Issue

Hello everyone,   I recently completed the Prepare for Your Salesforce Administrator Credential course and also completed  instructor-led class for ONE DAY . During registration for the instructor led, I was not asked to make any payment, and after completing the class, I received an exam voucher code automatically.  since I found and enrolled in the course on my own and was a bit confused by some FAQ information mentioning payment.  Has anyone experienced this? Or can someone from Salesforce confirm if this is expected behavior?  Thank you!