According to the pauli exclusion principle, the two elecrton present in same orbital must have opposite spin.
If the one electron is clockwise the other must be in anti clockwise direction. The clockwise direction is represented by the sign +1/2 while anti clockwise direction is represented by -1/2.
According the pauli principle, the two electrons must have different fourth electronic quantum number. The electron in same orbital have same first three quantum number i.e, n=1 l=0 and ml =0 in case of first subshell.
