The affix kha (īna) comes in the sense of 'reaching thereto' after the word āprapada,
The word प्रपद means 'the top of the foot'. आ means \upto\. आप्रपद is an Avyayibhava compound meaning 'to the top of the foot'. Thus आप्रपदं प्राप्नोति = आप्रपदीनः पटः 'cloth reaching to the end of the feet', i.e. showing the width of the cloth by comparison with the body.,