The exercise 9.17 of Language, Proof and Logic course goes like this:
Start a new sentence file, and enter translations of the following sentences. This time each translation will contain exactly one $\forall$ and no $\exists$.
- All dodecahedra are not small [Note: Most people find this sentence ambiguous. Can you find both readings? One starts with $\forall$, the other with $\neg$. Use the former, the one that means all the dodecahedra are either medium and large.]
I have passed the assignment successfully and my translation was: $$ \forall x (Dodec(x) \rightarrow \neg Small(x)) $$
My question is what is the other ambiguous interpretation for that English language sentence that authors hint on (the one that starts from $\neg$).
There is a well-known saying "All that glitters is not gold"
The literal translation of this would be:
$$\forall x(Glitters(x) \rightarrow \neg Gold(x))$$
but it is clear that what this saying really means is:
$$\neg \forall x(Glitters(x) \rightarrow Gold(x))$$
Maybe that's the 'ambiguity' they are referring to? Though I must say, I think the only reasonable interpretation of "All dodecahedra are not small" is what you have, and "All that glitters is not gold" is just a very poor way of saying "Not all that glitters is gold"