A blisk:

which contains no splitter blades or fillets, is represented as:

— hub
— shroud
— left blade
— right blade
An impeller:

Is represented as:

— hub
— left blade
— right blade
— splitter blade
— fillet for left blade
— fillet for splitter blade
— fillet for right blade
When defining your levels/sets they must contain the following surfaces:
.
.
,
, and
.
and
.
and
.
and
.