Why is the subjunctive necessary in this sentence?

Question

Aunque yo ________ lo que estás diciendo, no estoy de acuerdo contigo.Even though I understand what you are saying, I don't agree with you.(HINT: Conjugate "entender" in El Presente Subjuntivo.)The  correct answer is shown as "entienda", however, it sounds like the speaker is talking about  a known fact   and  in that case the present tense would work.  Or is the  rule that the verb after Aunque  is always in the subjunctive?

Accepted Answer

Hola Joanne
With "aunque" we actually use the present subjunctive when it is information that is known by the listener. You can also use the indicative "entiendo" if your intention is to present this bit of information as "new" for the listener. In this particular test-question we only accept the present subjunctive because it's a test about that conjugation as it says on the hint. Here's a lesson about aunque + pres.indicativo / pres.subjuntivo.
Saludos cordiales
Inma