How to update custom field for each invoice item by deluge ?

I have below code to try to update custom field named "Com".

When I run it, I get this error message

"{"code":15,"message":"Please ensure that the invoice_items has less than 100 characters."}"

The reason I tried this way is because I didn't find how to update only "Com" custom field for each item on invoice.

It's best If I can update only that field. (Please let me know If you know this way) but I couldn't find it.

So I just get all invoice_items field and then add new custom field inside then try to update but I get characters limit error.

Please help me if you know how to solve this issue.

Thank you.

invoiceID = invoice.get("invoice_id");
organizationID = organization.get("organization_id");
salesperson_name = invoice.get("salesperson_name");
invoice_items = invoice.get("invoice_items");
custom_fields = invoice.get("custom_fields");
sale_type = "";
for each item in custom_fields
{
label = item.get("label");
if(label == "Sale Type")
{
sale_type = item.get("value");
}
}
invoice_items = invoice.get("invoice_items");
new_invoice_items = List();
for each item in invoice_items
{
item_custom_fields = item.get("item_custom_fields");
type = "";
for each item2 in item_custom_fields
{
label = item2.get("label");
if(label == "Type")
{
type = item2.get("value");
}
}
product_name = item.get("name");
splitProductname = product_name.toList("-");
commision_detail = zoho.crm.searchRecords("commsions_structure","(Staff_Member.name:equals:" + salesperson_name + ") and (Product.name:equals:" + splitProductname.get(0) + ") and (Sale_Type:equals:" + sale_type + ") and (Type:equals:" + type + ")");
if(commision_detail.size() > 0)
{
commision = commision_detail.get(0).get("Commission");
}
CustomField = Map();
CustomField.put("label","Com");
CustomField.put("value",5);
item.put(CustomField);
new_invoice_items.add(item);
}
test = List();
test.add(new_invoice_items);
values = Map();
values.put("invoice_items",test);
response = zoho.invoice.update("Invoices",organizationID,"3878353000003769092",values,"zohoinvoice");
info response;