When selected, you can control the mesh density of curved features of the model by defining a chord angle.
The chord angle controls how closely the curve of the CAD model is approximated by straight sections in the mesh. The smaller the chord angle, the shorter the chord length, the finer the mesh. If the resulting chord length is greater than the general edge length, the general edge length will be used.
Using a Chord Angle will significantly increase the number of elements in the final mesh.