How to delete entries in the solarwinds license manager

I installed the ipmonitor v11.0.1 evaulation.and used solarwinds license manager to add ipmonitor free license.but after  I added it.I could not delete it.why? so the evaulation license and free license always exist there and cannot be choosed.How can I delete the entries in solarwinds license manager 4.0.17?