Lump 51 - Lightmap Pages …or Leaf Ambient Index HDR

This lump contains an array of dleafambientindex_t.

struct valvebsp.structs.lump_51.dleafambientindex_t
ambientSampleCount(int)<parsed from unsigned short>
firstAmbientSample(int)<parsed from unsigned short>

index into lump 55 or lump 56