The author has provided an equivalent alternative. After you've learned all variants, make sure to pause either the main line or the alternative. Pick your favorite for your review session. If you learn both and leave both active, you may have problems recalling the right move during review.

You can also skip these lines during learning sessions which will automatically pause it.

To pause, find and click the pause/learnt button at the top right of a variation or click 'Next' for more.