Hi June,
it seems these options are not created for this catalog item, but they are reference from Incident form Urgency field. You can see that if you switch to Type Specification field. So the proper answer is, you need to look at incident form and add the option to Urgency there. But I would not do that as Urgency (together with Impact) is used to automatically calculate Incident priority. So you would have to adjust that logic as well.
What you can do however, and I think would be better option is to add Impact to the form, so users can again choose Low/Medium/High, based on what system or how big a group of users is affected. This will then set you proper Incident priority.
We had a rule in my previous company, P1 incidents (Impact = high, Urgency = high) could however be only reported via phone to avoid unnecessary delay in noticing it, and it could be reported only by authorized personnel (e.g. team lead). Otherwise users start to abuse it. And if you have some SLAs connected with P1s you your users start sending you lots of P1s, you may very easily get into troubles.
