(You can join 2 times at once with the same Identity, useful for timing outs and listening to the music bot while you're in another channel).
Explain more plz 
At first you could only join 1 time per PC (to be more specific, per TeamSpeak identity), so when you try to join 2 times with the same PC (connecting in a new tab), it says that you can maximum join once.
Now the maximum is 2, you can join ambrosia teamspeak twice by using the option "connect in a new tab" and have 2 clients connected at the same time, example:

In the screenshot you can see that I'm connected twice, one in the Music channel and the other in a normal channel talking with my friends (oh wait I'm lonely).
Now the second thing useful, is that when you time out, TeamSpeak automatically connect you back again when you regain your connection. However, your first client doesn't disconnect immediately, it takes a few seconds, so this will happen:

Got it?