12 logas.

Explanation:

• In Śvetāmbara Sthānakvāsī Pakshik (fortnightly) Pratikraman—the one many people casually call “chaudās pratikaman”—the standard Kāyotsarga is 12 logas. One “loga” is the time it takes to recite the Logassa (Loggassa) Sūtra once. This measure is traditional and keeps the Pakshik Pratikraman shorter than Chaumāsī (20 logas) and Samvatsarī (40 logas). ( jainqq.org)

Note:

• Sthānakvāsīs usually do Pakshik Pratikraman on Pūrṇimā and Amāvasyā; some sanghs may do it on Chaudās, but the loga count for the fortnightly rite remains 12. ( jinavachan.blogspot.com)

For a simple overview of commonly recited Pratikraman sūtras, see this guide from JainKnowledge