well, the chance to get a c4 is 1/65, there are 33 c4, so the chance to get

is 1/2145.
you went into, say, 100 item-giving levels.. assuming you didn't get the antok ring, that chance is (1/2145)^2*(2144/2145)^98* 100 'above' 2 = 0,00103 = about 0,1% if i didn't make any mistakes
