I haven't used the interactive binning node for a while.
But to get 4 optimally binned groups, the Transform node is the way to go.
Add a Transform group node and specify Default Method for your inputs as Optimal Binning. Run! (the groups is 4 by default).
A much better alternative is Interactive Grouping node if you have licensed Credit Scoring for SAS Enterprise Miner.
Good luck,
Miguel