My heater works fine when I set the temperature to 69 and the temperature hits the desired temp it shuts off, then about 2 mins later the blower turns on like the heater is going to start up again, but since the desired temp is still satisfied the heater never comes on, the unit recognizes the fact that the system is satisfied so it then shuts off the blower.
Welcome to DIY!
The blower runs when the heat exchanger goes over a set temperature and turns off when it goes under it as I bet you already know. However, heat is still transferring from where the fire was burning so it can warm back up and turn back on for a minute or so. The blower doesn't care if your thermostat is satisfied or not as it goes by it's own temperature control to make sure the furnace doesn't get too hot. That is probably your issue.