Its not possible to use % symbol directly in the decision tree. You can follow this approach. You can use the divide function in the return area. Lets say you want to multiply the current value with 4% then you can do like (.currentvalue * (@divide(4,100)). The advantage of using the divide function is it returns the decimal value (4/100=0.04). If you use the normal expression like (.currentvalue * (4/100) it returns the value as zero because (4/100) always returns non-decimal value which is zero.