The affix ṭhac comes in the sense of 'this is whose act occurring in study' after a compound having polysyllabic word as a prior member.,
This debars ठक् ॥ Thus:- द्वादशान्यानि कर्माण्यध्ययने वृत्तानि अस्य = द्वादशान्यिकः 'an examinee who commits twelve mistakes in his reading'. So त्रयोदशान्यिकः, चतुर्दशान्यिकः ॥ The word अन्यत् in these sutras means the 'error', especially in accent, i. e. he who makes an accent अनुदात्त which ought to be udatta, or vice versa.,