Formula generating error:

if {@num Amounts} > 0 then
  sum ({GfCmps_1.GfCmps_1_Amount},{GfCmps_1.GfCmps_1_Campaign_ID})/{@num Amounts} * 100
else
  0

Cause of error: The field {GfCmps_1.GfCmps_1_Campaign_ID} used in the Sum function does not represent a grouping field.

Fix: Create a group on this
{GfCmps_1.GfCmps_1_Campaign_ID} field.