I think you are confused 1 Steem always = 1 Steem Power. as of this moment on Bittrex (the biggest external exchange that has functioning Steem wallets, Poloniex is failing Steem) is $1.83 SBD is $1.42 this is pretty normal difference and is actually maby little closer making it a better conversion, Steem was at $2.55 and SBD was at $1.90 at its recent peak I believe, anyway this is the conversion rate you want watch.