Sometime when you create a table you give is a descriptive name such as 'Serial Numbers' but realize a shorter name is more appropriate for the interface such as "SN" ( Especially when it appears on the left navigation icons.)
To change the name of an existing table follow these steps:
In ACT go the the TOOLS menu and select IMPACT
Click on the TABLES tab on the left side
Select your desired table
Click on the "Click Here to modify the tables's setting' button
On this 'Options'; form change the 'Display Name" of the table