An algorithm is currently processing box Current in the list: hence box from 1 to Current -1 are free. The procedure
void ALIAS_Free_Storage(int *Current,int *nb_box,int DimVar,int DimEq,
INTERVAL_MATRIX &Box,INTERVAL_MATRIX &GBox)
allows to free this unused storage by shifting: the box initially at
position Current will become box number 1.