The following table is a model suggesting you how could be defined a Priority Level.
The levels and their terminology of this model can be modified and adapted to your context.
It's built on 3 impact and 2 urgency levels, leading to 4 priority levels (as pre-configured in Octopus). Its impact criterion is based on a number of users. Use the following matrix as a sample to help you in establishing your own priority derivation Matrix. In Octopus, using the fields impact and urgency is optional to obtain a priority. We can evaluate the impact based on several criteria:
ATTENTION: Generally, priorities are defined and used to resolve incidents in an effective way it is not necessary to use priorities for Service Requests, as an execution target is to be defined for each Service Request type.