The breed standard says:
'Black with clearly defined markings as follows: a spot over each eye, on cheeks, as a strip around each side of muzzle, but not on bridge of nose, on throat, two clear triangles on either side of the breast bone, on forelegs from carpus downward to toes, on inside of rear legs from hock to toes, but not completely eliminating black from back of legs, under tail. Colour of markings from rich tan to mahogany and should not exceed 10 per cent of body colour. White marking is highly undesirable. Black pencil markings on toes are desirable. Undercoat is grey, fawn, or black.'
The pencil markings are not always present, and some breeds have markings on the feet that can resemble thumbprints. In some breeds they are a requirement, but in others they don't have to have them. They make absolutely no difference to the bloodlines/temperament of the dog, and within a litter some may have them and others not. When judging a show dog, these would be taken into account as a minor point, although they would be preferably on both feet the same.