Dongsheng,
Look at Ecoul and Elong when using ‘thermo multi’. I expect those are bigger numbers. Your 0.006 just means it’s kinda close to 0. I would not use 0 as an absolute reference… With respect to what number to expect, up or down, it depends on your system. Is it charge neutral? If so, then it depends on the spatial distribution of your charges whether your answer goes up or down with respect to your cutoff result.
Pieter