in 140 octets, it is possible to pack (140x8)/7=160 characters.
in 82 octets, it is possible to pack (82x8)/7 = 93.7, that is 93 characters. The 5 remaining bits are set to zero as stated above.
in 160 octets, is it possible to pack (160*8)/7 = 182.8, that is 182 characters. The remaining 6 bits are set to zero as stated above.
Do you understand?You can find the answer in 03.38.