Seeding can be active (data is sent to other peers) or passive (you are not sending anything). For torrent clients, both situations count as seeding.
The presence of peers that could not be connected is normal, maybe they closed their torrent clients few minutes ago, or they don't have open ports for torrenting. The latter situation make them unable to receive incoming TCP connections (only incoming UDP connections through punch hole are possible in this case). What you need to do to not have the same problem, is to check if the port used by Tixati is open. You can do it with the help of this website:
If you get Error:
I could not see your service on xxx.xxx.xxx.xxx on port (xxxxx), it means your incoming connections port is closed. You must open the port from your firewall, and do a port forwarding from your router. You can google how to use port forwarding for torrenting
to get more details.