وَمَرْفُوعًا إِذَا لَمْ يَكُنْ شَيْئًا مِنَ الْأَمْرَيْنِ: مُبْتَدَأً إِنْ لَمْ يَكُنْ ظَرْفًا، نَحْوُ: «كَمْ رَجُلًا أَخُوكَ» وَ«كَمْ رَجُلٍ ضَرَبْتَهُ»، وَخَبَرًا إِنْ كَانَ ظَرْفًا، نَحْوُ: «كَمْ يَوْمًا سَفَرُكَ» وَ«كَمْ شَهْرٍ صَوْمِي».
Translation: When kam is neither governed in the accusative way described nor made genitive by a preposition/iḍāfah, the book treats it as nominative. If not adverbial, it calls it a subject/topic; when expressing time, it is the predicate, as in “How many days is your journey?”
This slide follows the source’s classification. In particular, its analysis of «كَمْ رَجُلًا أَخُوكَ» as a nominative topic is the author’s account; other teaching traditions may describe predicative word order differently.