Otto needs $$2$$ tentacles to juggle up to $$3$$ balls. Using $$8=4\times2$$ tentacles, Otto can juggle up to $$4\times3 = 12$$ balls. 
Otto the octopus needs $$2$$ tentacles to juggle up to $$3$$ balls.  If Otto uses all $$8$$ tentacles, Otto can juggle up to  balls. 

  $$8$$ 
  $$9$$ 
  $$12$$ 
  $$24$$ 