Well I would say the extras are just a kind gesture as someone stated people want repeat customers. it's simple don't incubate them or if you get a friend started with that breed.
You also might consider another Thermometer just to be safe I run 3 in mine the probe one GQF sells a digital and then the type you have shown. The only 2 that stay close is the probe and the digi.
Keep in mind the text book for hatching is just that lol. I had my eggs see 120 for about an hour before I realized and brought them down. Eggs seem to be pretty resilient (Spelling). So don't stress to much. But glad you had movement....
Well there is a ton of variables. Other than making sure your temp is accurate and when lockdown comes your humidity is up where it needs to be it just could have been a bad hatch. I get those as a matter of fact I tossed out about 18...