What does the comma mean in m, c := E(K, m) Disclaimer: I'm a beginner to cryptography.

Background: I'm reading Cryptography Engineering by Ferguson, Schneier, and Kohno, where the authors use this image:



Question: What do the commas mean here?

My attempt: m, c :=  --- seems to mean "given" m, c equals ...
It's a comma to separate the two things.  Alice has $m$ and can calculate $c$ which is equal to $E(K_{e}, m)$.  Bob has $c$ and can calculate $m$ which is equal to $D(K_{e}, c)$.