It tells about electron orientation or spin which is clockwise, upspin or anticlockwise downspin.
As per Pauli’s exclusion principle, only 2 electrons with opposite spin can be filled in an orbital like 
Case I:
it has no electron because for there is no existence of orbital because orbital has so the value of should be 4 to have orbital.
Case II:
For : It has no electron because orbital are not present for .
Case III:
For it has maximum because subshell has orbitals and accommodates in each.
Case IV:
For it has a maximum of two electrons because an orbital can accommodate only two electrons with opposite spin.
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Case V:
For : it has maximum 6 electrons because the subshell has orbitals . Therefore each orbital can accommodate two electrons in each.