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