Hello. Again, I find myself stuck with a simple analytical problem

I am given a table of reduction potentials for various vanadium half-reactions relating to the speciation of vanadium in aqueous solutions and I am asked to find the most stable vanadium-containing species at pH 4 with all other conditions being standard. I calculated the potential of the hydrogen half-cell to be -0.236 at pH 4. To identify the most stable vanadium species, would I simply look for the half-reaction that has a value closest to -0.236?

The next question I am given asks to determine the pH range over which a 1 molar solution of VO

_{2}^{+} would be stable if all other conditions are standard. The reduction potential of VO

_{2}^{+} is 0.991. I calculated the pH that would be required to make the hydrogen half-cell potential 0.991 and found this to be 0.218. However, the question gives a hint that the required pH range is from acidic to slightly basic. I've checked my calculations over and they are all correct. I am thinking that my mistake here is a conceptual one. What conceptual mistake have I made?