This is the fifth of the five terms, or bounds, into which the Egyptian table divides Virgo. It runs from 28 degrees of the sign to 30, a stretch of 2 degrees held by Saturn. It opens where Mars's term closes at 28 degrees, and it closes the sign at 30 degrees, so Saturn holds the last 2 degrees of Virgo before the boundary into the next sign.
Set out in degree order, the five terms of Virgo run Mercury (0-7), Venus (7-17), Jupiter (17-21), Mars (21-28) and Saturn (28-30). At 2 degrees this is the narrowest of the five, against a widest of 10 held by Venus. The unevenness is not an accident of copying. No sign in the Egyptian table divides its five terms equally, and no two signs divide them the same way, which is why the table has to be consulted rather than derived.
The five rulers are the five planets visible to the naked eye. The sun and moon take no terms at all in this system, so each sign is shared out among Saturn, Jupiter, Mars, Venus and Mercury, every one of them holding exactly one stretch of it. A planet standing anywhere between 28 and 30 degrees of Virgo is standing in Saturn's bound, and Hellenistic technique reads the lord of the bound from the degree occupied rather than from the sign as a whole. The table this atlas follows is the Egyptian one, transmitted by Vettius Valens in his Anthologies and recorded by Claudius Ptolemy in the Tetrabiblos, which stayed in ordinary use after Ptolemy set out his objections to it and offered boundaries of his own.