I don't understand whats going on.  I expected the results to be:

Console.WriteLine above increment, count from 0 to 9.

Console.WriteLine below increment, count from 1 to 9.

Can someone please explain whats going on here?

Edit: Apparently I cannot add a picture\link

Code is:

let rec test x =
    if x < 10 then

        Console.WriteLine(x)

        test (x+1)
       
test 0

and

let rec test x =
    if x < 10 then

        test (x+1)

        Console.WriteLine(x)

test 0
In the second case where you get a count-down from 9 to 0, what's happening is the recursion bottoms out first, then you print as it unwinds.  Inlining the code to unroll the recursion, what you are executing looks like
let test x =
    if x < 10 then
        let x1 = x + 1
        if x1 < 10 then
          let x2 = x1 + 1
          if x2 lt 10 then
            let x3 = x2 + 1
              ...
            Console.WriteLine(x3)
          Console.WriteLine(x2)
         Console.WriteLine(x1)
        Console.WriteLine(x)which makes it obvious that the first line written is from the deepest call.