What is the meaning of 0 in a Cryosparc map

Dear All,

I wanted to ask a propabably very simple question, but that I need to be sure about,
In a map, how should I correctly interpret sections of the map that have values close to 0? I have a portion of my map that seems to have values of negative ESP and I wanted to ask if it’s proper to say that that specific area has a lower ESP than the background, and therefore the ice/solvent

This question stems directly from my lack of knowledge in this sense, but I can’t find a satisffying answer anywhere