Kurt Buhler comes up with a good rule:
Effective reports and dashboards should enable users to quickly answer their data questions so that they can focus on their primary business tasks and responsibilities. To help you design effective reports, we introduce the 3-30-300 rule for information design. The 3-30-300 rule is a straightforward and practical approach for you to produce efficient report layouts by structuring reports in a functionally hierarchical way. This rule concisely paraphrases the visual information-seeking mantra from Ben Schneidermann (1996). To make it easier to understand for Power BI developers, we express this rule with respect to approximately how long it should take users to get certain information or perform certain tasks in a report.
It’s a clever mnemonic and Kurt does a good job of showing how you could implement it.