What you're measuring doesn't makes sense on its own. For a SaaS product, a high number of registrations doesn't mean success. A high number of registrations, low churn and turning a profit means success.
As Andrew Grove's says in High Output Management, it's pivotal to pair metrics to avoid over optimising your business in the wrong ways:
- registrations (users in) → churn (users out)
- conversion rate (%) → new customers (absolute numbers)
- inventory count → # of times orders went unfulfilled