Found on stackoverflow:
http://stackoverflow.com/questions/40891532/is-memory-used-measured-in-bytes

In looking at the Maria DB documentation for Memory_used, I began wondering if it is somewhere documented that "all memory variables are measure in X" or something.

Is Memory_used measured in bytes? It would be of use to understand where that is mentioned in the documentation as well.

As the topic starter later found out, it is documented in MySQL Manual:
http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified

I think in the KB it should be documented also, either as a common-note (but maybe somehow more visible than in MySQL manual), or explicitly for each variable.