وَمَعْنَى جَمِيعِ الْمُدَّةِ، إِنْ صَلَحَ جَوَابًا لِـ«كَمْ»، نَحْوُ: «مَا رَأَيْتُهُ مُذْ أَوْ مُنْذُ يَوْمَانِ».
Translation: For the whole duration, when answering “how long?”, as in “I have not seen him for two days.”
When the answer measures how long, the entire elapsed span is intended. The book’s example uses nominative yawmāni, not the genitive form yawmaini.