ajaline , CID(caller identification) your phone logs incoming calls in it's memory. The #30 signifies that there are 30 CID(phone #'s) logged in the memory of phone from callers. The phone saves the information for the last 50 received calls to the CID list. The NEW icon marks any calls received since the last time you checked the list. You can delete these one by one or all by pressing ID (CID# will come up) then press menu/select button I believe 3x and repeat until all unwanted CID's are deleted. page 9-10 of the Dect 6.0 manual below may help. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
https://www.101phones.com/content/pdf/uniden/D1760.pdf