Just to add onto @amandavanceISC2's statement. If you watched a presentation prior to the date you received/renewed your CISSP, you can not count it. However, if you watch a presentation today, it counts, even if it was recorded prior to your start date.
One gotcha with Brighttalk is that the way that you watch the recording can mess up the auto-submission. See this post for details. Some of us manually add Brighttalk presentations right after we watch them and then go in later on to delete duplicates. Others keep an offline list and manually add missing entries a week or so later. Either method works; it is mostly an issue of personal preference.