If the slave does not respond to a message it is considered an error. If the slave does not respond to a retry it is another error. If the slave answers the next retry the error count would remain at two. If no more messages are missed the final result would be two errors. Any more missed messages add to the error count.
During the test the device may miss no more than 20 messages in total. If the device misses four messages in a row (one STX plus three retries) the test fails.