The fraction sitemap.xml/undefined as a percentage is NaN%. This result appears when the denominator is undefined, so the value cannot be expressed as a regular number.
In practical terms, a NaN% means the calculation doesn't produce a meaningful numeric outcome. It’s a placeholder that signals something went wrong in the data or the formula.
When you see NaN% in reports or logs, it’s a cue to check the source values—especially the denominator—to make sure everything is defined and properly formatted.