Note: There is no widely recognized IEC standard numbered exactly "IEC 949." It's possible you meant a different IEC standard (commonly cited ones in electronics and safety are IEC 60950, IEC 62368, IEC 61000 series, etc.). Below I expand on plausible interpretations and provide an engaging, expansive commentary framed for readers interested in international electrical/ICT safety standards and PDF reference materials.
: The adiabatic value is multiplied by this modifying factor to determine the actual permissible short-circuit current. iec 949 pdf