Months names are all one off?

[ReneZ]

I found a printed version of Sacrobosco's text. Hopefully, this link works (it seems so):

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This corresponds with fol 22r of the NKCR manuscript, i.e. immediately following the diagram shown by @nablator:
"Est autem Signum certa zodiaci portio duodecima..."
Here, the figure has the zodiac signs and the months offset corresponding with reality.
Does this mean that the Czech MS has a simplified drawing??