The sender writes...
Well when you say "zakuwam na okraglo" everyone understands that you study all the time. But when we think what these words mean literally, we also get another meaning and it is shown in the postcard (this is what woodpecker is doing). It is an idiom, so we don't translate it literally it’s only shown this way in the postcard to be more interesting and funny.
This postcard is postmarked from Poland in 2007.
I love how he is carving math problems into the tree ;-)