explain these 16 bytes on the stack

Expectation of sending strings from progmem to stdout would be zero ram consumption, using the advantages of the harvard architecture. It seems that sending a string from the array dont consume any memory, but sending the two large separated strings puts 8 bytes to the stack in this function, for every call, that are cleared after return, but still dont fulfill our expectations?

https://github.com/IngmarEckhardt/Dwarf-Example/blob/main/src/textfile_example_328.c