feeling like something is broken PPLNS, does it amplify variance?

4242 7 0.00000170538367  / 354 = .48 (=52% negative variance from PPS)
4241 8 0.00000194691120 / 354 =   .55 (=45% negative variance from PPS)
 4240 9 0.00000218239581  / 354 = .615
 4239 11 0.00000266574438  / 354 = .75
 4238 13 0.00000314915633  / 354 = .89
 4237 13 0.00000314915633  /354 = .89
 4236 13 0.00000314445819  / 354 = .887