What’s your coding background? More details on how you’re looking to interact with this would be helpful. Fortunately, Glutanimate wrote out really nice variable names so everything is pretty easy to follow even if you don’t have much coding experience
Days learned is the percent of days that had a learning or re-learning card shown.
Streaks are defined as a continuous pattern of review activity spanning several days. Neither the type of activity nor the intensity are factored in. As long as you review some cards on a day, that day will be counted towards your streak. If you miss a day of reviews, you have broken the streak.
I’m not sure what true retention is. I don’t see it in Anki. Maybe its from another plugin?