Human Design adapts the chakra model, and the adaptation is not one to one. The classical scheme most often cited in modern Western usage has seven centres. The bodygraph has nine.
Where this one lines up
The Head sits at the top of the bodygraph and corresponds in position to the crown centre of the classical seven, the highest of that scheme. This is one of the centres where the correspondence is straightforward: same position, comparable role as the topmost point of the series.
What the numbers mean
Two of the bodygraph's nine, the G or Identity centre and the Spleen, have no counterpart in the classical seven at all. They are additions. The rest correspond roughly by position, though not always by function.
Recording that arithmetic is the honest way to describe the borrowing. Human Design does not present a chakra system; it presents a nine-centre model that took its starting point from one.
The other side of the comparison
The sevenfold chakra scheme is itself a simplification. Indian tantric traditions describe chakra systems with varying numbers of centres, and the standard seven of modern Western usage is one arrangement among several that circulated. A reader comparing nine with seven is comparing a 1987 construction with a modern popular rendering rather than with an unchanging original.
Human Design was published by Ra Uru Hu in 1987 and is recorded here as a contemporary system.
Sources Rainbow Body: A History of the Western Chakra System from Blavatsky to BrennanKurt Leland with The Origins of Yoga and Tantra: Indic Religions to the Thirteenth CenturyGeoffrey Samuel, The Human Design SystemRa Uru Hu (Alan Robert Krakower)