Over many years creating dashboards for our clients we have found that no matter the business there will always be some level of ambiguity around the true meaning of metrics on a dashboard.
This is only natural, given the varying terminology, different departments and lines of businesses operate in the day-to-day. As dashboard designers our job is to ensure all report audiences are on the same page when interpreting a dashboard, that's why we always include a metric glossary with our dashboards.
For example, you have a standard operation which should take 5 days. Is that 5 business days or 5 calendar days? Does day 1 count as 1 or 0? Do bank holidays count? A seemingly simple metric can be quite intricate behind the scenes, and it's critical that everyone understands this.
If you have a key business system that you're reporting off, does everyone use the system in the same way, and are some users not filling in fields, being less thorough with their usage? These are prerequisites to creating any dashboard, and any metric rules like this must be included in a glossary.
We always say that confidence in a report is only one mistake away - if you make an error in report development, it can completely alter how the report is seen throughout the business. This is another reason to include a glossary - it instils confidence with the report audience that what they are reading is correct and well thought out. It also means fewer people will switch off if they don't understand the report.