Did the Power items lose value?

I was Ev training my Zoroark. I would write down my ev progress on paper and use the serebii ev value for each pokemon. I would check and she would say that it could work harder. Am I nuts or am I not doing something right? Or are other people having similar issues.

Please use the question threads in your Pokémon game's forum when asking questions about game mechanics (i.e. post in BW2's Quick Questions thread for questions about BW2). The Battle Center only allows questions strictly related to battling or team building (i.e. "How do I improve my prediction skills?", "How can I fix my team's weakness?", "What EVs should my Pokémon have?", etc.), and this is question about the Pokémon game itself.