The extended pentatonic scale that begins on the 5th string, intersects the next three positions.
The MINOR TONIC within the 5th string extended pentatonic is the very first note--in this case, A. So, therefore, this is in the key of Am.
The MAJOR TONIC within the 5th string extended pentatonic is the second note--in this case, C. So, therefore, this is also in the key of C.
Below is an example of the 6th and 5th string versions of the extended pentatonic scale in action (In the key of Am/C).