Case 1: A person leaves to use the toilet and returns once finished. This falls within the expressed necessity exception.
Case 2: A person leaves purely to wander through a market. This is an unexcused exit, not the bodily-necessity exception.
The school disagreement about duration applies to the second category.
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Bab al-Iʿtikaf: Rules, Restrictions, Invalidation and Vows
Case 1: A person leaves to use the toilet and returns once finished. This falls within the expressed necessity exception.
Case 2: A person leaves purely to wander through a market. This is an unexcused exit, not the bodily-necessity exception.
The school disagreement about duration applies to the second category.