The book says: بِالْمُضَافِ إِلَى يَاءِ الْمُتَكَلِّمِ غَيْرِ جَمْعِ الْمُذَكَّرِ السَّالِمِ.
Translation: A noun annexed to the speaker’s yāʾ, excluding the sound masculine plural.
The sound masculine plural uses wāw/yāʾ letter markers, as learned in the prior lesson. Do not automatically treat its special possessive forms like the singular غُلَامِي.
For this lesson, retain the explicit exception in the source rule.