The first is the personal madhhab.

The second is the conventional madhhab.

Among later scholars, when they say, “This is the madhhab of al-Shafi‘i,” or Ahmad, or the like, what is generally meant is the conventional madhhab. Indeed, the imam himself may hold a view contrary to what is designated as his madhhab, yet they regard as his madhhab that which they have conventionally established.

What the author means here by “the madhhab of Ahmad” is the conventional madhhab.

“Perhaps I have omitted from it issues that rarely arise, and added matters upon whose like reliance is placed; …”

His statement, “Perhaps I have omitted from it issues”: “it” refers to al-Muqni‘.

Issues is the plural of issue. An issue is that for which evidence is sought in a field of knowledge. Hence they say: knowledge consists of evidences and issues. Evidences are textual—if they are a text from the Quran, the sunnah, or scholarly consensus—or rational—if they consist of analogy.

His statement, “that rarely arise,” means: those that occur infrequently, because one should not occupy oneself with rare issues.

His statement, “and added matters upon whose like reliance is placed”: “what” is a relative pronoun, meaning “that which,” and its relative clause is “reliance is placed.” “Upon whose like” is connected to “reliance is placed.” The meaning is: I added important issues upon which reliance may be placed.

Thus, this book contains three matters:

The first: limiting itself to a single view.

The second: omitting rare issues.