The UK Parliament constituency of County Galway was an historic Irish constituency, comprised the whole of County Galway, except for the Borough of Galway. It replaced the pre-Act of Union Parliament of Ireland constituency. Its representatives sat in the British House of Commons.
The UK Parliament constituency of County Galway did not consist of all of County Galway
It is correct because it says it consisted of all of County Galway, except for one Borough. The syntax in the context is kind of odd, which is why the system got it wrwong