Inaccurate SLA reports

[j.jackson]

Hello Community,

I am having an issue with my SLA reports. I have an excel that I use to combine all SLA's, Created vs Resolved, etc. In Jira, I have an SLA and Created vs Resolved for each department. I take the averages from JIRA then put them into the spreadsheet and calculate the averages for the department as a whole.

I have a report in JIRA service Desk that should be showing me the averages for the JSD as well. My issue though is that the numbers are completely different. I use the Past Year by month for all the departments:

The order of the report is: Critical, High, Medium, Low , Average

Dept1:  

Dept2:

Dept3:

Averages should be something like. .74 , 21.90 , 16.08 , 5.98 , 14.44

However, When I do the SLA averages as a whole for JIRA, the numbers are drastically different. 

As you can see, for High the averages are 11.78, but using the averages by dept. shows 21.90

As a note: Tickets are assigned to dept. based on Security level. I use level = XXX to create the reports.

I checked each series and all have same logic to remove Test tickets, so even if they were incorrect logically, data should still be consistent. I even tried changing the logic so it specifically calculated the averages for those 3 departments, nothing changed. So what em I missing? these numbers are very inaccurate and I don't know which report to believe.