«وَمِنْ صُوَرِ بَيَانِ التَّغْيِيرِ: الِاسْتِثْنَاءُ»
“Among the forms of modification is exception.”
An exception initially mentions a quantity or group and then removes part of it by illa. Thus, “ten dirhams except three” acknowledges seven dirhams.
Under the Hanafi analysis, the initial statement is construed as having been made only about the remainder after the exception: the speaker is treated as acknowledging the residual amount. Under the Shafii analysis described here, the initial formulation provides a basis for the whole before the exception restricts its effect.
The difference lies in how the legal effect of the utterance is analyzed, even where both schools accept the same simple arithmetic result.