Hi, what exactly are you trying to understand with the report? If you are looking to see any proofs that have been opened at any time, try a document report. I was messing around with using 'proofing progress' filter, has to be a way to pull these with this info but I'm not getting it on initial tries.
If you are looking to see if someone has opened a specific proof, you can see that in the Proofing Workflow tab of a Proof (SOCD = Sent/Opened/Comment/Decision)
Or can get more detailed look in the Proofing Activities tab of the proof: