Rebalancing is the process of periodically reviewing and updating the constituents of a smallcase. You can see the next expected update date on the smallcase page under the Stocks & Weights tab
This is done to ensure the stocks & weights in the smallcase continue to reflect the underlying theme and model
When a smallcase you hold has been rebalanced, you receive a Rebalance Update notification for the same via e-mail
You can now see the changes made by the update, make changes if you wish to and then apply them.
Note: Making changes to the rebalance update means it will no longer match the original version. Only proceed with making changes, if you're 100% sure. Not recommended for first-timers :)
If you do not rebalance your smallcase with the update, your smallcase holdings, composition & returns may vary from the original. Also, your smallcase will not reflect the underlying theme/model as intended