Use Recursion to Create a Range of Numbers

From this image I found, I would like to know if
in (2), will the recursion always add 1 (lo+1) to the lo until it gets to the end of the number defined in the syntax (hi-1) and then push the (hi)

i don’t think that is the meaning.
It is hard to explain it here though. Do you know how to use a debugger? If you write the code and then put a breakpoint on the function, you can see it working and step through it line by line.

There’s no operation that adds 1 to lo in their algorithm. They’re just illustrating that the number that comes after lo in the array is equal to lo + 1. So if lo is 1, then first item in the range is 1, and the second is 2.