وقال أبو يوسف: خمسة أرطال وثلث رطل
Translation: Abu Yusuf says that one saʿ is five and one-third ratls.
This is a difference in the historical weight of a saʿ: eight Iraqi ratls in the earlier view, versus five and one-third ratls according to Abu Yusuf.
It is separate from the rule that wheat uses half a saʿ and the other three foods use a full saʿ. Do not mistake a disagreement over measurement for a disagreement over which foods are listed.