m36five Great question! This can vary a lot based on length of video, audience, and a few other factors. For my weekly Top Of Mind videos, I'll typically see 65-80% retention. I try to keep those videos 3-5 minutes and fast moving. That includes and audience that largely knows me, though not all of them are working directly on Stream or video.
My short tips for better retention:
Keep it short. Target 3-5 minutes tops.
Know your audience - try to cover topics you know they have been asking about in other forums
Use chapters to give people hints of what is coming and keep them tuned in
Use the Stream Screen recorder/Camera to include on-screen titles that show what you are talking about
Try some things out, measure it, and see what works!