What do A pos and C pos mean?
The # column is the rank of each listed entry for Astrophysical Journal, Supplement Series — rank 1 means this entry is where Astrophysical Journal, Supplement Series has the most articles or citations. A pos and C pos show the reciprocal: the position of Astrophysical Journal, Supplement Series within that entry's own ranked list, by articles and citations respectively. A low value means Astrophysical Journal, Supplement Series is among the most prominent contributors for that entry.