There are two different versions of the TB SEO score you see on the Video watch page on YouTube: SEO Studio Score & General SEO Score.
SEO Studio Score Version
If it's one of your videos that you've applied an SEO Studio optimization to, you should see the SEO Studio score version since we know the Target Keyword because there's an optimization tied to the video.
The SEO Studio score version breakdown should look similar to the one below if you hover over it. This score is the percentage of these elements which are noted best practices for search engine optimization. The more that these best practices are achieved in the video, the higher the SEO Score will be.
General SEO Score Version
If it's a video where we don't know the Target Keyword, we show a general SEO Score. You'll see this version for videos belonging to other channels or videos of yours where an SEO Studio optimization hasn't been applied. This is why someone may see a lower score for your video even when you’ve applied SEO Studio Optimization to it despite seeing a higher score yourself (others viewing your channel are not logged into your TubeBuddy account where the score is calculated differently in SEO Studio because there is a target keyword).
The general SEO score - in contrast to the SEO Studio Version score - is a percentage calculated from the elements listed when you hover over the score in YouTube (Tags in Title & Description, Tags in Title, Tags in Description, Total Tag Characters, and Title Words in Description). Note that this is a shorter list of best practices because the target keyword is unknown (without a target keyword, the formula instead pulls from the tags that are already listed for the video), and therefore only about half of the best practices suggested for search engine optimization are able to be considered to produce the score.