This is not related to the number of records returned by the CRM. It depends on if the contact is in 3CX contacts when the call is sent to the phone. For example, if the call goes first to a queue, and then to the extension, then most probably the CRM lookup will return a value fast enough to add it to the 3CX phonebook before the call is sent to the extension. But if the call is sent to the phone as soon as it arrives to 3CX, without other entities between, then the contact will not be available when the call is sent to the phone.