Depths don't seem to calculate correctly

[Malwhynn]

Starting from my base on the first level, the depth shown with my avatar is 217 fathoms. I open the mapstone and choose a location in the third deep that is listed as 165 fathoms below. I expect, therefore, the new depth to be 382 fathoms. When I check the depth at this location is says 300 fathoms. This is consistent between multiple attempts to travel via mapstones; the starting depth and the distance(delta depth) to the new locaton don't actually add up to depth at that new location. The distance to the new location appears to be off by about a factor of two. Is this something that can be fixed, please.