If using callerID, which is what you have indicated, the info to display such is coming between rings one and two. This is standard in the US and each ring is 2 seconds of ring followed by 4 seconds of silence. You as a caller hear a ring sooner as the system has to wait for the CID info and then route the call. Until the system sees the CID info, the call is not displayed as active.
If you dial a number from a phone, then you need to press dial/send/etc. to cause the phone to dial immediately, otherwise; the phone will wait for a timeout (anticipating more digits) and then dial. Additionally, there may be a delay before the UCM will send the call out the line as it has to seize the line and depending on the FXO dial delay setting, may wait for the allotted time before calling. I notice that yours is set to “0” which may not be a good idea. Maybe you have no issue in which case leave it alone, but -
When you have a regular analog telephone and take the receiver off-hook, this seizes the line, but there is a physical delay that you likely induce by raising the handset to your ear to see if dialtone is present. This delay gives the line time to settle as there may be a small period of time before the line is truly ready to start taking digits which could result in miss-dials. If you do have issues at some point, I suggest you putset to 500 which is 1/2 second and see if it helps.