The source illustrates number tamyīz with «عِشْرُونَ دِرْهَمًا», not a universal rule for every numeral.
Additional comparison: «ثَلَاثَةُ كُتُبٍ» uses genitive iḍāfa, whereas «عِشْرُونَ كِتَابًا» uses accusative tamyīz.
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Important Limitation: Number Constructions
At-Tamyīz: Clarifying Quantities and Sentence Relations
The source illustrates number tamyīz with «عِشْرُونَ دِرْهَمًا», not a universal rule for every numeral.
Additional comparison: «ثَلَاثَةُ كُتُبٍ» uses genitive iḍāfa, whereas «عِشْرُونَ كِتَابًا» uses accusative tamyīz.