Ptolemy's fourth quarter, the southwest of the inhabited world, is the one he calls Libya, and he puts it in familiarity with the water triplicity, Cancer, Scorpio and Pisces. The lands he lists are the Mediterranean and Saharan north: Numidia, Carthage, Mauretania, Gaetulia and their neighbours.
That list is the whole of Africa as the scheme knows it. Ptolemy's inhabited world stops well short of the equator, and everything south of the Sahara lies outside the frame the chorography divides. So the quarter a modern retelling labels Africa covers a strip along the top of the continent, and the great majority of the landmass, along with every tradition that grew up in it, has no place in the system at all.
Egypt is the exception, and it is a large one. Egypt sits in the scheme with sign assignments of its own, and Egyptian material is woven through Hellenistic astrology at a far deeper level than the chorography suggests. The decans, the thirty six ten degree divisions of the zodiac, are an Egyptian construction taken into the Greek system, and the pseudonymous attribution of astrological texts to Egyptian authorities was a standard feature of the literature.
The atlas records both facts side by side, because they pull in opposite directions and both are true. The technique owes Egypt a great deal, and the technique's own map of the world barely sees the continent Egypt sits on.
Sources TetrabiblosClaudius Ptolemy with A History of Western AstrologyNicholas Campion