Count samples are in 'case' and 'control' groups. You can count 'homozygous', 'heterozygous' or 'any' variants. Case and control are defined by a string containing plus and minus symbols ('+' and '-') where '+' is case and '-' is control. This command adds two annotations to the VCF file.

For details about this tool, please go to http://snpeff.sourceforge.net/SnpSift.html#casecontrol