An initial letter, with a final it letter as a final, is the name of itself and of the intervening letters.,
This sutra explains the mode of interpreting pratyaharas. Thus the pratyahara अक् means those letters whose beginning is अ and whose final इत् is क्.
Why do we say with 'the final indicatory letter?' Because a pratyahara like सुट् would be otherwise ambiguous. It might be doubted whether it is formed with the final ट् of औट् and refers to the first five case-affixes, or whether it is formed with the initial ट् of टा and therefore refers to the first seven case-affixes. The present sutra clears up the doubt. A pratyahara is formed with the final इत् and not with the initial इत्.,