Apparently the instructions have been updated since the above comments, because they now call for the CR1620, which is what I bought, and they work perfectly!
The instructions and photos are very clear, easy to follow, and accurate. I was very pleased to find this site and realize that for about 15 bucks total I could replace the batteries in both our 2010 Outback keys - I had imagined we'd have to get new keys or at the least take them to the dealer for a highly pricey replacement. Thanks, ifixit!!