When is a low CR too low?

Getting my feet wet with CPA and social marketing, and I'm browsing through my various CPA publisher accounts looking for offers that jive with the various forms of social maketing I have going on. I understand what a conversion rate is, but how do I know when the CR is too low? Obviously there is a huge difference between an offer with a 45% CR and one with a 7% CR, but I'm confused on exactly why similar offers have such different conversion rates? Am I reading it wrong?

The offer conversion rates are based on how they marketed it- your conversion rate is based all on how you market it to potential customers. Higher conversion = more profit and a better sales representation vs. a low CR which is just meaning you are mediocre marketer... some conversion rates are just low because the offer sucks.