After thalāthata, the counted noun is plural genitive in a construct. After ʿishrīna, it is singular accusative specification.
Opening interactive controls...
The Case of Counted Nouns
Choosing the Correct Parsing: Meaning, Governance and Context
After thalāthata, the counted noun is plural genitive in a construct. After ʿishrīna, it is singular accusative specification.