Are there metrics to show management the need for more resources?

I have a new scrum team that I have been assigned to that feels that they need more people on their team. Management has told them that they need to show that they need more people on their team through metrics in Jira. I have done a couple of sprints with the team and as a team we have gotten their capacity and velocity to a good level. However this team does operational work and project work. about 55% is operational work which comes in daily and 45% is project work. Both operational and project work is captured in Jira.