Converting 'deprecated' LODDistance to new StaticSize and DisplayFactor

What do StaticSize (on static meshes) and DisplayFactor (on skeletal meshes) represent ? FBX Importer used to respect the threshold values set on eLODGroup when importing, but now it just ignores it. For skeletal meshes it always just did DisplayFactor = 1.0f / (MaxLODLevel * LODIndex), which gives me wrong result on some meshes i have with specifically selected LOD Distances.

I have seen that ConvertLegacyLODDistance function in StaticMesh still respects LOD Distance for older meshes imported back when it was supported, so why is this same conversion not done on newly imported meshes ? How do i do the calculation manually to have correct ScreenSize and DisplayFactor ?

Let’s say i have LOD Distances of 1500,2500,6000,12000,24000 (1500 being for LOD 0, the highest poly mesh). Must DisplayFactor be 1.0f for the highest poly mesh ? If so, what does the 1500 mean, then ?