فَإِذَا زَادَتْ عَلَى الْأَرْبَعِينَ: وَجَبَ فِي الزِّيَادَةِ بِقَدْرِ ذَلِكَ إِلَى سِتِّينَ عِنْدَ أَبِي حَنِيفَةَ رَحِمَهُ اللَّهُ، فَفِي الْوَاحِدَةِ: رُبْعُ عُشْرِ مُسِنَّةٍ، وَفِي الِاثْنَتَيْنِ: نِصْفُ عُشْرِ مُسِنَّةٍ، وَفِي الثَّلَاثِ: ثَلَاثَةُ أَرْبَاعِ عُشْرِ مُسِنَّةٍ.
Translation: When cattle increase beyond forty, Abu Hanifah holds that zakat accrues proportionately on the increase until sixty: one additional cow entails one fortieth of a musinnah, two entail two fortieths, and three entail three fortieths.
According to Abu Hanifah, an increase above 40 but below 60 is not wholly ignored: an additional proportional share of a musinnah becomes due for each added cow.
Rub‘ ‘ushr means a quarter of one tenth, i.e. one fortieth. Accordingly, two extra cattle give two fortieths and three give three fortieths of a musinnah.