26 Songs is every song from that session. 6 Songs was released first, then later 8 Songs came out, which was different recordings of the 6 songs on 6 Songs at the same session, plus 2 other songs. 10 Songs is the same songs from 8 Songs plus two bonus tracks that were recorded at the session. When they were looking into reissuing/remastering the tracks they couldn't find the masters from 6 Songs so they used a vinyl copy that Dale had.
