After the verb kram , preceded by upa and para , when used in the senses of 'continuity', 'energy' and 'development', the ātmanepada is used.,
The words vritti &c., of the last sutra are understood here also. Why has this been made a separate sutra and not included in the last? The reason is to make a restrictive rule in the cases of upasargas; that is to say, only in the cases of the upasargas upa and para, there is atmanepada affix; but not so when any other upasarga precedes the verb kram, though the sense may be of continuity &c. Thus उपक्रमते 'he commences to advance,' पराक्रमते 'he marches to attack.'
Why do we say after the upasargas 'upa and para'? Because, after any other preposition the affix will be of the parasmaipada; as संक्रामति 'he makes progress.' If the sense is not that of \continuity\ &c., parasmaipada will be employed, as उपक्रामति, पराक्रामति.,