In game tabs are restricted to these rules:
< 3h: 1 wave
3-6h: 2 waves
6-12h: 3 waves
> 12h: 4 waves
If you have a target > 12h then you have 4 waves land at 00:00:00.
If you then upgrade the Tournament Square again, you can again send 4 waves to land at 00:00:00
With this you can have way more than the 4 wave limit land at the exact same second.
Yes, I know that. You can also have more than 1/2/3 waves in <3/3-6h/6-12h range with that trick. I just wanted to point out that it's legal to do that and that it's also legal to use multiple browser tabs for sending.