How can I get all unique records from the last hour from Potentials?

I try url= https://crm.zoho.com/crm/private/json/Potentials/getRecords?newFormat=1&authtoken=".$token."&scope=crmapi&lastModifiedTime=".date('Y-m-d H:00:00').

But I have only 20 (or 200, if I add params "&fromIndex=1&toIndex=200" to request).