The affixes taught in prāgvateṣṭhañ [[5.1.18]] etc. have the sense of 'this is its measure'.,
The word तद् shows that the word in construction should be in the nominative case. Thus प्रस्थः परिमाणमस्य = प्रास्थिको राशिः 'a heap whose mass is a Prastha.' So also खारीकः, शत्यः, शतिकः, साहस्रः, द्रौणिकः, कौडविकः, वार्षशतिकः, वार्षसहस्रिकः ॥ So also षष्ठिर्जीवित परिमाणमस्य षाष्ठिकः, द्विसाप्ततिकः ॥
Why the words तदस्य have been repeated in this sutra, when their anuvritti could have been drawn from the last aphorism, the word सोऽस्य and तदस्य being the same? The repetition shows that the affixes are again ordained, so that the elision taught in 5.1.28 does not apply. Thus द्वे षष्ठी परिमाणमस्य = द्विषाष्ठकः, द्विसाप्ततिकः, ॥ Here the affix is not elided by 5.1.28.,