When you're on RNG Reporter, look at the choices of methods. You'll find one that says Wondercard IVs. Put your seed in, choose wondercard IVs, hit generate, find your spread on the list. Now switch to Method 1 as your method and hit generate, see where your spread is on the list. Compare the two and you will probably discover why you had a difference in frames last time.
Edit: if you want a perfect spread with a low frame, try this seed 7b100958. Since Mew's nature can be anything, there's no reason to use a seed with a high frame, unless you like low delays. But this one has a low delay anyhow.
PID: 685011a9 (MODEST, ability 1) 31/31/31/31/31/31 (Seed: 7b100958 Method 1: 24, J (synch): 5, J (no synch): None, K (synch): 3, K (no synch): None) HP DARK 70