question on addTile argument flags

[lukasvd]

In DtNavMesh.cs addTile is defined as

public DtStatus AddTile(DtMeshData data, int flags, long lastRef, out long result)

In DtMeshSetReader.cs the method is called with i as a tileIndex (and provided to the argument "flags")

mesh.AddTile(data, i, tileHeader.tileRef, out _);

than in the method tileIndex is extracted by means of "int tileIndex = DecodePolyIdTile(lastRef);"

I am a bit confused by this, could someone explain the function of flags (it is commented as > Tile flags. (See: #dtTileFlags), but I can't find this reference).