Unspecified ʿamm: no member has been removed through valid specification. The source assigns it definite indication and requires action upon its meaning.
Specified ʿamm: some cases are removed by evidence. The text continues to govern the remainder, while further specification is possible and the indication is considered presumptive.
Example 1: ma tayassara min al-Qur’an — the book’s illustration of unspecified generality.
Example 2: reading ahalla Allahu al-bayʿ together with harrama al-riba — the book’s illustration of specified generality.
The sequence is: identify the general expression, then establish whether and how its scope has been specified.