It is not necessary to specify the number of lines; the conference will automatically accommodate your meeting participants up to a maximum of 1000 callers (accessing your conference via phone). You can elect to send invitations as well, but doing so is an optional feature. Once scheduled, feel free to send out the call information to anyone you would like to join the conference.
For more information about large-sized conferences, please fill out the form at the following link: https://www.freeconference.com/landing/request-host-large-calls/
Additionally, free accounts also offer up to 5 web conference participants, all of which are able to share their video and/or screens. With a paid subscription, up to 100 web participants can join via internet and 8 of those would be able to share their video or screen. You can find out more about our paid plans here: https://www.freeconference.com/pricing#compare.