It means that the library you are opening uses Modeica Standard Library 3.2.3 and SystemModeler 4.3 supports and ships with 3.2.1.
However, if the library doesn't use any of the new components from 3.2.3 it probably works fine with 3.2.1.
Otto
Thank you! I've posted another bigger problem - SM 4.3 not compiling even with manual entry for clang++ and SDK on Mac OSX 10.14. Your help is appreciated!!
gani -