Why does the Spectre octopus only have 7 tentacles?

The answer is almost certainly related to aesthetics rather than any deeper meaning. The logo has been portrayed inconsistently throughout the Bond franchise, with the octopus starting out as a quadropus, then becoming a proper octopus, and most recently, being rendered a septopus. Many Bond fans argue that the original Dr. No/From Russia With Love design, with four "legs", was never supposed to be an octopus, and was intended to represent a ghost; according to these fans, the franchise mistakenly turned the ghost into an octopus in Thunderball. The image itself lends some credence to the idea that the original logo was a skull with ghostly trails below, but I haven't been able to find any canonical references to support it.

Note that in the new design:

• The octopus is more stylized than was the case in the previous logo, more sinister, less cartoonish, and less obvious.

• The octopus is drawn in such a way that it also resembles an actual spectre, or ghost.

• The new design is sleeker, more modern, and combines the symmetry of the previous, eight-legged design, with the menace of the original design, which looked as much like a skull as it did a cephalopod.

Additional motivation to change the logo was introduced by the MCU, and its SPECTRE analogue, HYDRA:

^{SPECTRE left, HYDRA right}

The film's producers would certainly want to avoid any confusion between the two logos.

Or perhaps the latest incarnation of SPECTRE is fond of the so called "Seven Armed Octopus", which gets its name from the fact that the specialized tentacle used in reproduction is kept hidden from sight in males of this species.

It may be a rather mundane matter of aesthetics. An eight-tentacled version of the same insignia might have seemed too "busy" or "heavy," design-wise, to the moviemakers. An eight-tentacled version would also look like an octopus, whereas the seven-tentacled version suggests an octopus, and the moviemakers (or, if you like, SPECTRE's design staff) may have opted for the subtler, sneakier option.

During the movie 'Spectre', there are 7 subordinates with one at the top. It worked for the movie. It may change over time in the future, to fit the needs of the series. The leader, the bad guy was caught not killed.

The actual reason is because drawing 8 instead of technically 6 and a body was more doable in a short time, and with 8 they couldn't really have a central one, so it boils down to easy of drawing it. sorry if you wanted a real 007 plot thickening answer, there isn't one P.S I cant give my name as i am an official source, Steve, Pinewood Art dept

I noticed a similarity between the reichsadler tunic ornaments on the Bust of Charlemagne and the Spectre Octopus. Trying to suss out a connection, I found your question.

Sorry, I suppose this is more speculation. That said, one could suppose that art direction could choose to echo nazi co-opting of heraldic motifs in order to give everyone the willies. Good art directors grok to dat iconography.