public int mask { get; set; }

The index at which the binary representation of the integer contains a bit turned on is the number of the area type.

If the query proceeds uninterrupted to the target position, the represents the area type of the NavMesh polygon where the resulting NavMeshHit.position lies.

When the query terminates at the edge of a NavMesh polygon that is of a different type than the ones allowed by the input parameters, the represents the area type of the polygon that blocks the query.

When the query terminates at an edge of the NavMesh the is 0, to signify that there is no polygon beyond that position.