The move from Old to Middle Indo-Aryan generated aspirated palatals in quantity. Inherited clusters of a stop with a sibilant, and clusters of several other shapes besides, resolved into this sound as the language simplified its consonant groups, so a word that shows a cluster in Sanskrit will very often show this single aspirated palatal in the Prakrit of the Ashokan edicts. The letter is accordingly frequent in the earliest surviving Brahmi, and more frequent there than in a classical Sanskrit text of the same length.
That difference between the two stages of the language is one of the things the Ashokan material is most valuable for. The edicts were cut across an empire that stretched from the northwest to the far south, in several different Middle Indo-Aryan dialects, and the dialects differ from one another in exactly such treatments: which clusters resolved to what, which vowels were kept apart, whether an inherited r appears as r or as l. Comparing the same edict as it was cut in different places is therefore a linguistic experiment the Mauryan chancery ran without meaning to, and it remains the earliest direct evidence for dialect variation anywhere in the subcontinent.
The letter is also a good illustration of why a transliterated text is not a substitute for the original. The two-letter roman spelling used for it suggests a cluster of a stop and a breath, and a reader who has only seen the transliteration will assemble the sound wrongly and will also miscount the syllables, which matters as soon as verse is involved. The Brahmi sign is one letter for one sound, and reading the script rather than a romanisation of it settles both questions at once.