RPM drop notes should start with the denominator

A creator RPM drop needs view base, traffic source, geography, and content mix before layout changes.

When a creator sees RPM drop, I want the denominator written down before any layout change. Which view base is being used? Did traffic source, geography, content mix, or device mix change? Is the creator reading RPM, CPM, page RPM, or session RPM? A layout test can be useful, but if the denominator changed first, moving ad slots may only make the evidence harder to interpret.