Up until this discussion, I've never heard of X total cM being 392. I suppose it could be looked at that way, but I consider a "full" X match to be 196+/- whether it is male or female. For calculating cM values of matching segments (both autosomal and X), GEDmatch calculates both half-identical and full identical IBD in the same manner - based on the start and end positions of the segment. The chromosome graphic that is shown in some of the utilities shows individual SNPs as either green (full) or yellow (half) depending on whether it is a half or full identical match, but that does not affect the resulting cM value of the matching segment.