Reading this table
The three temperature columns are the conductor's insulation rating, not the ambient temperature. A 90°C-rated conductor is not permitted to run hotter than the equipment it terminates on allows — and most breakers and equipment are listed for 60°C or 75°C. In practice the 75°C column governs most installations, and the 90°C column is used as the starting point for derating rather than as a final ampacity.
The overcurrent cap column
The smallest conductors carry a fixed protection ceiling that is separate from ampacity. It exists because small conductors have little thermal mass and are easily damaged, and it applies regardless of what the temperature columns read. The cited section carries specific exceptions this table does not reproduce.
Before you use these numbers
Correct for ambient temperature and adjust for the number of current-carrying conductors before sizing anything — see the temperature correction and bundling adjustment tables, or let the ampacity lookup apply both.