Bah, I screwed myself a little bit doing this. I bought 12+6 months to top off my Xbox Live which had 19.5 months on it. But I couldn't redeem the 6 months because the maximum Xbox Live you can have is 36 months. So I converted over what I had, but now have a 6-month Xbox live card that will only convert to 2 months of Game Pass.
Moral of the story: you cannot exceed 36 months of Xbox live. Plan your purchases accordingly so you aren't stuck with Xbox Live cards that are less valuable!
Moral of the story: you cannot exceed 36 months of Xbox live. Plan your purchases accordingly so you aren't stuck with Xbox Live cards that are less valuable!