DVD Subtitle Encoder uses MS Windows API for font creation. Every font in MS Windows is described by LOGFONT structure.
C-language definition of LOGFONT structure is as follows:

typedef struct tagLOGFONT {
  LONG lfHeight;
  LONG lfWidth;
  LONG lfEscapement;
  LONG lfOrientation;
  LONG lfWeight;
  BYTE lfItalic;
  BYTE lfUnderline;
  BYTE lfStrikeOut;
  BYTE lfCharSet;
  BYTE lfOutPrecision;
  BYTE lfClipPrecision;
  BYTE lfQuality;
  BYTE lfPitchAndFamily;
  TCHAR lfFaceName[LF_FACESIZE];
} LOGFONT;

For DVDSupEncode are important mainly lfFaceName and lfCharSet which define letter shape and also national character set.
These two values are taken from parameters FontName and FontCharSet (specified either in DVDSupEncode.ini or directly in source text).