DMARC compliance ratio is calculated by dividing the number of emails that passed DMARC authentication by the total number of messages sent from your domain.
An email is considered passed DMARC when it passes either SPF evaluation and/or DKIM evaluation.
To comply with DMARC through SPF, you need to use a custom SPF domain (Return-Path domain or “Mail FROM” domain), because SPF validation requires the domain in the “From” address to match the SPF domain. By using your own SPF domain, you have the flexibility to use SPF, DKIM, or both to achieve DMARC validation.
Learn more about DMARC:
The Ultimate Guide to DMARC Reporting
Why Every Business Needs DMARC