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