Hello satya suravit

your problem has nothing to do with available phsyical memory(RAM) in your CPU, but rather with the amount/number of variables that you intend to modify at the same time.
Allow me to suggest you click on the "Help" button on the message popup which will tell you the following and hopefully answers your question:

Description of Error:

The number of variables to be modified is too large to modify all visible variables.
The variables that cannot be modified are identified with the symbol.

To Correct or Avoid Error:

- Click the "Yes" button:
Any variables that are not identified with the symboland are visible will be modified.
- Click the "No" button:
No modification takes place. You can use the Modify Value as Comment context menu command to deactivate the display of individual modify values.