Subscribe to all the messages with mosquitto or open your MQTT client software:
sudo mosquitto_sub -t +/# -v
The value is between 0 and 1024 and is tranmitted via Mqtt when it changes.
You will receive every TimeBetweenReadingDHT (set into config_DHT.h) the DHT measurement (30s per default).
If you want to don't resend value when it is the same you can set dht_always = false in config_DHT.h