Real comprehensiveness (istighrāq ḥaqīqī) includes every member of the relevant class. Customary comprehensiveness (istighrāq ʿurfī) includes the whole set understood within a context. “جَمَعَ الْأَمِيرُ الصَّاغَةَ” (The ruler gathered the goldsmiths) can refer to all the goldsmiths under discussion, not every goldsmith in the world.
The source further distinguishes singular from plural negation:
“لَا رَجُلَ فِي الدَّارِ” — Not even one man is in the house.
“لَا رِجَالَ فِي الدَّارِ” — There is no group of men in the house. On the discussed reading, the plural negation can remain true with one or two men present; the singular negation cannot.
A definite class expression need not imply an unlimited universal claim. Accepted customary boundaries can delimit its scope.