KW Autoresponder (AND ANY OTHER APP) can only know for certain if it sent a text.
We use native android mechanism for sms sending. The texts are sent to your carrier and back we get one of the three statuses – Sent, Error, Sending. Then your carrier should deliver it to the recipient.
Unfortunately there is no way to validate delivery.
So when KW Autoresponder says it has sent a message it has just sent it to your carrier.
So the statuses in the Reports say if the text was successfully sent (to) / received (by) your carrier.
There are a lot of reasons why it may never get received.