The difficulties associated with evaluating the efficiency of treatment in mental hospitals in the 19th century provide a vivid example of how numbers become a stumbling block when used for official evaluation of institutions. The evasion of assessment due to private interests or because of corruption tends to make these numbers “funny” in the sense of becoming dishonest, while the mismatch between boring, technical appearances and cunning backstage manipulations supplies dark humor. The article focuses on the various ways in which medical clinics and government agencies as well as large companies manipulate numbers for the sake of improving performance and finding objective facts. The author examines and analyzes the practices of classification, standardization and ordering of the parameters by which the performance of a particular structure is assessed, while also questioning the relevance of these number-based practices as an assessment tool. The article cites as an example the various tricks resorted to by directors of treatment centers for the mentally ill in order to improve performance and claim that most of their patients are healthy when discharged. The hidden ambivalence of numbers, their deceptiveness and their unsuitability for resolving contradictions and unifying experience based on statistical data are demonstrated. The concept of a thin description is also introduced, which implies an unambiguous interpretation of funny numbers and using them as an argument for evaluating efficiency. The dangers are evident in recent efforts to decentralize the functions of governments and corporations by using incentives based on quantified targets.