I think this is intentional. It looks like it's the database ID for the particular stat cat you're adding entries to.
The Hard Due Dates and Z39.50 Servers admin pages also have this.
It would be more useful if Evergreen displayed the name of the stat cat rather than the database ID.
From what I can see Hard Due Date also displays database ID but Z39.50 Servers shows the name of the source you are adding attributes to.
I think this is intentional. It looks like it's the database ID for the particular stat cat you're adding entries to.
The Hard Due Dates and Z39.50 Servers admin pages also have this.
It would be more useful if Evergreen displayed the name of the stat cat rather than the database ID.
From what I can see Hard Due Date also displays database ID but Z39.50 Servers shows the name of the source you are adding attributes to.