Filter Invoices by Custom Fields

Filter Invoices by Custom Fields

I need a list of invoices in Zoho Books based on the value of a custom field - all invoices with a value of 35 in the custom field. 

This is my current code: sOrgId = organization.get("organization_id").toString();
CustomF = Map();
iValue = 35;
CustomF.put("customfield_id","2575294000004994047");
CustomF.put("value",35);
response = zoho.books.getRecords("Invoices",sOrgId,CustomF,"zbooks2");
info response;

The problem is that it doesn't only give me the invoices with that value - it returns all the invoices.

How do I fix this?