DNS question

The instructions for setting the Ethernet WAN & Cellular WAN DNS servers reads “DNS Servers Select a DNS server for this port to use. This port can either be automatically selected or manually designated.”

However, I just noticed that the firmware allows you to check both boxes at once, as shown below:

So, my question is, when both boxes are checked as shown above, is the router able to use all of those DNS servers, or is it just using one subset? (i.e. Is it just the auto ones or just the manual ones?)

We will choose the first two DNS server which will and in your case.