One division of the Chaturthamsha spans 7 degrees 30 minutes, four to a sign and forty eight in the zodiac. The ascendant crosses that arc in roughly half an hour, so the D-4 remains readable from a birth time known only to the nearest ten or fifteen minutes.
The four divisions of a sign are assigned to that sign and to the fourth, seventh and tenth from it, the four angles counted from the sign itself. The construction mirrors in miniature what the chart is for: the angles of a horoscope are the fixed points of a life, and the D-4 is read for the fixed things a person holds, land, buildings, the home and property in general.
Where the D-4 sits in the scheme matters to how much weight a reading should give it. It is not one of the shadvarga, not one of the saptavarga and not one of the dashavarga. It enters only in the full shodashavarga of sixteen, alongside the D-20, D-24, D-27, D-40 and D-45. That places it among the specialised charts, consulted when the question is specifically about property rather than folded into a general estimate of a planet's strength.
The practical consequence is that a D-4 reading should be offered as an answer to a narrow question, not as a second opinion on the nativity as a whole.