Unfortunately it seems that the widget always shows the total count of requests (opened + closed..).

If you change the filter of Service Catalog > My Request Filter to grab only the Requests in an open state, when you click the "X Requests" on the Employee Center you will find out that you can only see those filtered items. So you wouldn't be able to see any record on the "Closed Requests" option.

My workaround, although I still didn't figure out if there is a simple way how to do it (currently testing), is:

• Go to Employee Center > Activity Configuration;
• Clone the Requests record and deactivate the original one. You can even change the name to something like "My Requests";
• Create a simple script include, that makes a query to the sc_request table with the filter you want and return the getRowCount() value;
• On the entry "My Requests" change the summary view script to the new script include

I hope that this helps. If I figure out another way, I'll also share it here.