[Chimera-users] Electrostatic potential values at each residue

Dear All, I'd like to get the electrostatic potential (ESP) values at each residue in a protein. I implemented the "Coulombic Surface Coloring", then get the distribution of ESP values at each residue by "Render/Select by Attribute" (Attributes of [residues], Select -> Attribute [value_Coulombic_ESP]). However, The surface plot and the ESP values obtained by "Render/Select by Attribute" do not coincide with each other. For example, there are some residues where the surface plot reports positive ESP values, while "Render/Select by Attribute" gives negative ones (e.g. VAL70 CG2 in the Chimera session file attached.). Could you teach me how to solve this discrepancy? Thank you very much in advance, T.M.