I'm assuming you mean numbering of tasks here
If you have Reporting turned on in your WF project (check Add Process Component on the Reporting tab of Project Properties), you can specify a prefix (in your case it's be IT) and a Pad Length (in your case I believe it would be 4). However, the slash character will be a hyphen: IT-0001.
To do this just on the stream, you'd just use some String Handling components to build the number:
Add New Data Element component to add a string "IT\"
Add New Data Element component to add your integer counter... starting at 1
Pad Text component to pad with 0's
Merge Text component to merge your prefix with your padded counter.
Hope that makes sense.