@eisfunke @Cykelero @jakehamilton the actual use of the variable is to count the number of seconds since the bash instance was started - you don't have to assign anything to it but assigning a value resets it to that value (and it normally only works with the uppercase SECONDS).

Bash also offers $RANDOM (you can guess what it does) as well as $EPOCHSECONDS and $EPOCHREALTIME for the more exotic ones.

And.. many more (https://www.gnu.org/software/bash/manual/bash.html#Bash-Variables)