When in the Interest Calculator if running a calculation the Law Society de Minimus figure this can be changed in a setting on the Accounts Administration.
When in the Accounts Administration, select the SYSTEM SETTINGS tab at the top.
Select the Misc tab.
There is a setting that is called 'De Minimus value for Interest Calculator' if you select UPDATE.
Amend the value in the box and this will be the amount that comes through on the Interest Calculator screen.
Select SAVE.
NB
This is only available in version 3.5.1.07 and above, if you don't have this version you will require an upgrade for the change.