[Alneyan]

Alternatively, claim only some systems, resulting in bogus borders. To alter your borders, go to the Score screen => Borders. If you want to claim the whole galaxy, click on every systems you are not already claiming (you will miss some if you are not an Ancient player, unless you are very patient).

The Ancient race can also see how many colonies the enemy has in total, by looking at the appropriate figure in the Planets screen. This does not always work, however, and is mostly useful if there are only a couple of Empires in the game. Regular Empires can usually get the same information, but only about the enemy colonies present in systems they have seen. I am not sure what may prevent that figure from working though.