CR stands for Conversion Rate. CR simply means the average Conversion Rate. The idea behind CR is to give you an idea on how the offer is performing compared to other offers on WOW Trk.
The Conversion Rate is not a guarantee of how the offer will perform if you run it. The Conversion Rate for example on an offer in 'Top Offers' in your account is simply the average across the network so you can see how that offer is performing.
You can also see the Conversion Rate of an offer in your personal reports, this rate is the rate you are averaging.