Board Game Arena

Hi, if i put my cursor over the event pile it says:

A: 3 coins per each development track point
B: 2 ...
C: 1 ...

but I could no find anything about this A B C in the rule book. When do I get what?

The A, B, C is at the top of the event tile for the round.

Now the events have been revisited in later printings (before there were no A, B, C tiles. So make sure you refer the latest rules (the correct English and German rules are linked on the game page)