some more data from eeprom inside the cards
If you only give half a question you can only expect half an answer.
I wrote something like "byte data[2048];" for a atmega328 board and the compiler didn't see any wrong with it.
That is right as far as the compiler is concerned their is nothing wrong with it.
You can even write
byte data[63000] and the compiler will not blink at all. Just try using all the bytes though and see how far you get.
is it possible to estimate memory usage of a sketch?
Yes add them up.