Six at the beginning means:
If an inferior element has wormed its way in, it must be energetically checked at once. By consistently checking it, bad effects can be avoided. If it is allowed to take its course, misfortune is bound to result; the insignificance of that which creeps in should not be a temptation to underrate it.
A pig that is still young and lean cannot rage around much, but after it has eaten its fill and become strong, its true nature comes out if it has not previously been curbed.