Brackets are not supported as a way to control processing order, the processing order is fixed as *, /, +, -, MIN, MAX
If you want to use * and - in the same calculation, for example you need 20% of the result, then you will need to use the calculation below as a * calculation will be calculated first.
[INVOICECHARGESNUM][*]0.2[-][INVOICESECONDITEMNUM][*]0.2[-][COMMISSIONNUM][*]0.2
=== Rounding and controlling decimal places ===