How to count number of lines with the same dimension value?

Hey

Is there anyone who knows if you can count the number of lines with the same dimension value, in this case "Tjenestenummer"?

I have a table that has two dimension values - "Alder" and "Tjenestenummer". Since counting occurs over a period of one year, "Tjenestenummer" can be in two age groups. For example, an employee is 29 years old at the start period and 30 years old at the end period. I can count how many age groups there are, but for example, I would like to be able to count that "Tjenestenummer" 14445 has two lines.

The column in the example counts which number age group it is.