edit server ip address

Hi, i did do a ticket for the last month but now that i really start to use this, it does not make sense to me so i wanted to post on here for clarification.

Here are the details, When i was on my old server i had three IP addresses NS1 NS2 and DED (all different). Now that my reseller host has moved me to a new server for better response time i only have two IP addresses

i will just give the last two here for simplication

13 for ns1
14 for ns2

but 14 is also my ded ip address as well.

So when i go into edit server on WHMCS it shows

Name
Hostname
IP address

For the ip i was told by WHMCS to put the shared ip in there which is 13 but that does not make sense because when i click on WHM button it attempts to login to 13 not 14.

So i thought ok i will put 14 in there, but thats not my shared its my ded IP, actually its both i guess i dont know.

So my questions are, what goes in that input, ded, shared, does it really matter?
Can i put the ded ip in there so i can use the WHM button?
Will using the ded ip in there mess with my clients registration at all?

Just need some clarification, thanks.