The word puṇya has acute accent (udātta) on the final when preceded by a Noun in the Locative -7th case.,
Thus अध्ययने पुण्यम् = अध्ययनपुण्य꣡म्, वेदपुण्य꣡म् ॥ The compounding takes place by 2.1.40 by the process of splitting the sutra (yoga-vibhaga), taking सप्तमी there as a full sutra, and शौण्डैः another. Here by 6.2.2, the first member would have preserved its accent, the present sutra supersedes that and ordains acute on the final. The word पुण्य is derived by the Unadi affix यत् (Unadi V. 15) and would have retained its natural accent 6.1.213 and thus get acute on the first syllable by krit-accent. 6.2.139. Why do we say 'a locative case'? Observe वेदेन पुण्यं = वेदपुण्यम् ॥,