It works with misc field form the Directory-->Company-->you need to create one user per set (as person and associate the extension to it) -->in person config -->Miscellaneous--> Misc.1 -->your code
I believe you wanted to tag the employee’s number on their extensions and display it on the generated reports. If that’s the case, as alternative solution, you may use other parameters listed on the Extension’s Properties tab. Go to Reporting-->Account./traf.-->Organization tab-->NMC. For example, let’s make useful of the parameter "Postal Code" then input the employee’s number and apply the changes. Please take note that "Postal Code" is defined as Zip Code on Report’s Querytool. After, configure your report definition having the parameter "Zip Code" from the Querytool then rename the Field Label as Employee Number. Once done, generate your report.