When using overset tools, a new column appears (shown below) in the Set BC panel after selecting an overset assembler (Grid, Overset, Attributes). This column provides the ability to choose the Overset Type to assign to that particular boundary condition. The types provided correspond to the selected overset assembler. As with other boundary condition entry edits, you can double click the desired row and choose a new type from the pull-down list.

CAE, Set Overset Boundary Conditions
Another column appears when an overset assembler has been selected.