Asmoday commands seventy-two legions. In a catalogue whose defining feature is its own count of seventy-two, that is unlikely to be coincidence, and it is one of the few internal patterns in the book that looks deliberate.
The number seventy-two carries weight independently across the traditions the Lemegeton draws on. The Shem ha-Mephorash is seventy-two-fold. The Letter of Aristeas has seventy-two translators produce the Greek Pentateuch. The table of nations in Genesis was counted as seventy or seventy-two depending on the textual tradition followed, and the sending out of the disciples in Luke is seventy in some manuscripts and seventy-two in others. Seventy-two is five degrees of the zodiac multiplied out to the full circle, which is the arithmetic underlying the decan attributions the Golden Dawn later applied to both the angels and the spirits.
Weyer's text already asserts seventy-two kings in the brazen vessel while listing sixty-nine, so the number was attached to this material before the Lemegeton's compiler set to work. What the Lemegeton did was make the enumeration match the assertion.
Whether the seventy-two legions in this entry were placed here to echo that, or inherited from a source, cannot be recovered. Weyer's Sydonay, his form of the name, also commands seventy-two legions, so the figure predates the Lemegeton at least by that step.
The caution worth attaching is that patterns of this kind are easy to find in any list of numbers, and the catalogue supplies dozens of them. This one is more striking than most because the number is the number of the book. It remains an observation about the text rather than an explanation of it.