How to reconcile this hadith with the hadith of Aisha (may Allah be pleased with her) in which the night prayer is eleven rak'ahs?

The questioner : Shaykh, are ... eleven rak'ahs at night ... do the other rawatib (regular voluntary prayers) count as a sunnah (recommended practice)? It is a sunnah.

The Shaykh : No, sometimes and sometimes. I mean, if one takes the hadith of Aisha he omits the sunnah of Fajr or omits the two light rak'ahs with which he used to begin the night prayer. And if one counts the two light rak'ahs, it becomes thirteen. Yes.