Seroquel Vs. Seroquel XR?

I have been on Seroquel 100 mg at night for anxiety and to help me sleep. A few days ago my doctor gave me samples of Seroquel XR 50 mg. He gave these to me just because he didn't want to right me a whole new prescription (insurance reasons) He wasn't very clear on what I was supposed to take. So my question is, do you think that I am supposed to take two 50 mg Seroquel Xr?