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