Do you always get so defensive when you are the one that made the mistake? You said packs which means more than one. You did not say pack which means one you said packs thereby sounding like it was more than one. So the person in the wrong is you by using the wrong wording. When it is one you use the singular form of the word and no one would think you meant more than one. When you use a plural form of a word it therefore leads anyone reading it to think you mean more than one.
So by what you state she was correct in thinking you meant more than one since you said packs (the plural form of pack).
And purchasing more than one at 160cc each implies PACKS. Quit being pedantic and argumentative.