According to the MIB's own description, this object's meaning depends on which sub-category a given table row represents: for rows tagged with the maxSpeed sub-category it holds the highest recorded speed of the indexed fan, while for rows tagged minSpeed it holds that fan's lowest recorded speed. An admin must first check the row's FanRPMHealthSubCategory value before interpreting this number, since the same object name means opposite things (a historical high versus a historical low) depending on that context. For example, a row indexed as minSpeed reporting 900 rpm means the fan has never spun slower than 900, whereas the same value under a maxSpeed row would instead mean the fan has never exceeded 900.