Translation:They have lived here for ten years.
Since no detailed explanations on grammar are being given we are looking for them elsewhere and those contradict what you are teaching us.
" E: I have already lived in London for 10 years. D: Ik woon al 10 jaar in Londen.
Here you see one difference when using ‘already’ (D: al). As you can see, in Dutch a regular present simple is used to make this sentence correct. Why? Dutch counts that you are living there a long time and you still do, so at present you are living there and since it’s a long time, it’s a habit. So: present simple.<pre>
D: Ik heb 10 jaar in Londen gewoond. E: I have lived in London for 10 years.</pre>
As you can see from the example above, you CAN actually use PP in Dutch but than it specifically means that you DO NOT live there any more."
Maybe the Duolingo sentence meant exactly that - they no longer live there, but then "already" and "for ten years" become a problem.