Since the graphics scale is a dynamic block just select it, right mouse click and on the context menu that appears select Block Editor
In the Block Editor on the ribbon's Visibility panel click on Visibility States

In the Visibility States list box that appears select 1" = 30'-0"
Click Set current button
Click New button
In the Visibility state name edit box enter: 1" = 40'-0"
Make sure the last radio button is selected click the OK button

Back in the Visibility States window with the newly added 1" = 40'-0" checked click Move Up button so that it's listed under 1" = 30'-0" then click the OK button

Select the two numbers 30' and 60' then click on Edit > Copy with Base Point or Ctrl+Shift+C

For base point enter: 0,0
Then hit the Delete key on the keyboard to Erase both of those numbers
Then on the Visibility panel select from the drop down list 1" = 30'-0"
Enter keyboard combination Ctrl+V to paste those two numbers back at 0,0
Then on the Visibility panel this time select from the drop down list 1" = 40'-0"
Enter keyboard combination Ctrl+V to paste those two numbers back at 0,0 again
Then double click each number and edit them accordingly to reflect 40' and 80'

Finally click the Close Block Editor button on the ribbon and at the alert window select Save the changes

Now back in the drawing window you can select the graphic block and there's now the newly added 1" = 40'-0" selection
