The affix aṇ comes in the sense of 'its modification or its part' after the words bilva etc.,
This debars अञ् and मयट् ॥ Thus बैल्वः 'the modification or part of Bilwa'. The word गवेधूकाः occurs in this list. It would have taken 'an' by the next sutra also; its inclusion in the class of Bilwadi is for the sake of preventing the application of मयट् to this word.
I, बिल्व, 2 व्रीहि, 3 काण्ड, 4 मुद्ग, 5 मसूर, 6 गोधूम, 7 इक्षु, 8 वेणु, 9 गवेधुका, 10 कर्पासी 11 पाटली; 12 कर्कन्धू, 13 कुटीर.,