How are raw data calculated? (vs PowerLab)


As I understand, for every position (AF7, AF8, TP9, TP10) we got a column of data (channel) in muse file (RAW_AF7, etc). But in PowerLab, in for the same positions, we got only two channel of data, where for instance channel 1 it would be RAW_AF7-RAW_AF8…

So, are RAW columns calculated making a difference with somthing??