Final answer:
Stephen's reports for the Ammary Corporation are best characterized by their complexity, being detailed but not easily understandable by others. This underscores the necessity of clarity and accessibility in business reporting.
Step-by-step explanation:
The reports prepared by Stephen for the Ammary Corporation, which has an activity-based costing system, are described as being long and full of facts, yet difficult to understand by anyone but Stephen himself. The characteristic that best describes Stephen's reports is complexity. These reports, while thorough, are not effectively communicating the necessary information in a manner that is accessible or clear to the intended audience. This highlights the importance of adhering to principles such as Conventions, Clarity, and Coherence when preparing reports, as mentioned in the Analytical Report: Writing from Facts.
Additionally, in the context of costing and business reporting, understanding the Lessons from Alternative Measures of Costs is critical, as it allows for a breakdown into fixed cost, marginal cost, average total cost, and average variable cost, providing valuable insights into the financials of a firm.