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