If I understand you correctly I don't see a problem. I'm not sure about the "right way" and "wrong way" If your connections are like this you should be OK:

Internet=>Modem=>Router=>HT-502

Above is how I have my network configured. Some people experience problems having the ATA behind their router. I made a few changes to my Netgear router's config. so it could handle VOIP traffic. To avoid router problems you can put the ATA between the modem and router like this:

Internet=>Modem=>HT-502=>Router

If your phone is working with the ATA plugged into one of your routers LAN ports all is well. Be happy.