We must be careful here and pay attention to the grammar.
The word here is not Jug or Yug but Yuge.
ਜੁਗਿ Yuge means in the Yug, in the age, in the era.
ਜੁਗਿ ਜੁਗਿ yuge yuge - in each age, in each era...
So Guru Hari Gobind ji is not giving the number of Gurus that will be follow him. In fact...