Hi Nur Fadhilah
You can't multiply a list like this. You need to give it a value. From IteratorTagValueC, multiply the C value, also change varaiable inside "ValueCpRODUCT =" no need
$ValueCProduct * IteratorTagValue/C(Attribute)
If you have a value to be filtered in the filter, you should do it outside the loop and then return the filtered one.