How can the seven characters equal the six character Nam-myoho-renge-kyo?

"Now I, Nichiren, have inherited the seven characters Nam-myoho-renge-kyo within the treasure tower and in this era of the Latter Day of the Law I work to disseminate them throughout Japan." -- SGI/NST dishonest translation.

"Now I, Nichiren, have inherited the seven characters Namu-myoho-renge-kyo within the treasure tower and in this era of the Latter Day of the Law I work to disseminate them throughout Japan." --  accurate translation