وَحُكْمُهُ فِي كَوْنِهِ مُفْرَدًا أَوْ جُمْلَةً، مَعْرِفَةً أَوْ نَكِرَةً، كَحُكْمِ خَبَرِ الْمُبْتَدَإِ.
Translation: The same rules that apply to a normal mubtadaʾ’s khabar—whether single-word or clausal, definite or indefinite—apply to the khabar of inna.
This directly continues Level 28: single-word and clausal predicates remain possible, while the initial governed noun becomes accusative.