Hi Yeni -
From your configuration, you will have 16 concurrent web sessions (6 with the original bundle plus 10 extra with the MPE-PLUS10-W order). Will all 16 teachers also be using voice sessions during the web? If so, this would leave you with only 4 voice sessions. Another thing to note in the MPE configuration, not licensing. By default, when a user schedules a voice conference, web sessions are also scheduled. This may not be what you want. In the MPE configuration you can specify whether web sessions are automatically reserved or not. This will allow you to retain the web sessions for those users authorized to schedule them. I doubt you will need 50 web sessions, but I would canvas your teacher community and see how many of each sessions they anticipate using. For example, we have 70 voice sessions and 26 web sessions. Another configuration option is to reserve so many voice sessions per "conference". By modifying this value, you can ensure your voice sessions are not oversubscribed.
Ginger