成唯識論了義燈 2.48

2.48

問：既許四大造極微，一微中已有四微，若准七微，各有其四合二十八。何故但言七成拏，并四大合有百四十？

Question: Since it is accepted that the four great elements create paramāṇus, in one paramāṇu there are already four paramāṇus; according to the seven paramāṇus, each having four, there are twenty-eight in total. Why do they only say seven form an aṇu, which together with the four great elements would make one hundred and forty?