G2-item #0
Let:
  T1 = {:index 178266, :time 71733263293, :type :ok, :process 15, :f :txn, :value [[:r 2691 [85 86 87]] [:r 2691 [85 86 87]] [:r 2650 nil] [:r 2703 [53 56 57]]]}
  T2 = {:index 178227, :time 39956291251, :type :ok, :process 39, :f :txn, :value [[:append 2650 134] [:append 2650 135] [:r 2703 nil]]}
  T3 = {:index 178260, :time 71656303784, :type :ok, :process 12, :f :txn, :value [[:append 2691 85] [:append 2691 86] [:append 2703 53]]}
  T4 = {:index 178262, :time 71726067093, :type :ok, :process 15, :f :txn, :value [[:r 2691 [85 86]] [:append 2691 87] [:append 2703 56]]}

Then:
  - T1 < T2, because T1 observed the initial (nil) state of 2650, which T2 created by appending 134.
  - T2 < T3, because T2 observed the initial (nil) state of 2703, which T3 created by appending 53.
  - T3 < T4, because T4 appended 87 after T3 appended 86 to 2691.
  - However, T4 < T1, because T1 observed T4's append of 87 to key 2691: a contradiction!