It looks like “The Tandra Collection” is partially wrong. It leaves the C-# format numbering sequence and Book 9 as currently listed in the Core is wrong and/or incomplete.
Each “Book” is a series of issues that are numbered as 9, 9b, 9c etc. on the cover are ACTUALLY given C-## issue numbers. This was partially correct, but then it changed to the numbers on the covers which may or may not reflect the actual issue number.
So, for instance, Book 9 is labelled 9, 9b, 9c on the covers:
but these are actually C-25, C26, C-27
I have submitted #25 (which is incorrectly listed as #9), #26, and #27 to core if that helps, though there is no longer a way to make it C-25, C-26, C-27, etc.
Tandra
#25 Book 9 AndelKrag
1986
Hanthercraft Publications
Adventure, Fantasy
Color|USA|English
9.4
Andelkrag (C-25)
Magazine
$1.75