Let's say Adam has 10 apples. If Beth asks Adam how many apples Adam has, and Adam replies I have 7 apples, would that be a lie or a true statement?
In defense of Adam: It is true that he has 7 apples, however he also has an 8th, 9th, and 10th apple in addition to that.
In critique of Adam: It would be misleading to suggest that he has any less than the exact total of 10 apples. One could argue that Adam would be able to say he has 0 apples, which seems like it should be wrong.
So is Adam right or wrong? Does the question need to explicitly ask for the total amount of apples he has in order for his statement of 7 apples to be false?
What Adam said is true, but it was not the answer to Beth's question.
Check out the Gricean Maxims for more insight as to how people expect other people to engage in communication with them. I would consider Adam to have violated "Make your contribution as informative as is required" and "Avoid ambiguity".
You have also noticed that "zero" doesn't work like other numbers in common language, and I have met some people (admittedly students of classical philosophy) who maintained that "zero" was not a number. Again, this is how language works, not how math works.