Can someone explain me in detail what means this bonus. I don't understand it
When you develop a technology in the last column, you get a victory bonus based on how many of a certain resource you have. For example, if you develop rockets, you get 3 Victory Points for every Gem you control (where you have a city or meeple).
The CN tower lets you use another player’s controlled symbols to compute that bonus.
For example, let’s say you develop Rocketry and you have control of 2 gem symbols. You would score 6 points. However, if you have the CN tower, and another player had 4 gems, you could count their gems instead when you develop rocketry and score 12 points.
Does that help?