It remains Excel or a pencil and a piece of paper :) Greetings from Luboń :)

Hello warmly
Can someone explain to me how it is
Since I bought cryptocurrencies X for 100 dollars at the level of 3.00$
Later I bought again for 100 dollars at 2.81$
Later I bought again for 100$ at 2.70$ ...
So how on earth did the platform calculate that my average purchase price is 2.43$
Can someone explain to me where the problem is, I don't understand something????