Random number generator not random in a batch file

Trying to generate a random number and use it for variable value in Windows batch script file. Maybe I am missing something very basic, but something is not working here for me.

Created a batch file named random_test.bat with the following content.

SET rnumber=%random%
echo %random%
pause

Running the file consecutively three times produces the following set of outputs:

One

C:\Users\user\Desktop>SET rnumber=28955

C:\Users\user\Desktop>echo 20160
20160

C:\Users\user\Desktop>pause
Press any key to continue . . .

Two

C:\Users\user\Desktop>SET rnumber=29072

C:\Users\user\Desktop>echo 13887
13887

C:\Users\user\Desktop>pause
Press any key to continue . . .

Three

C:\Users\user\Desktop>SET rnumber=29183

C:\Users\user\Desktop>echo 18885
18885

C:\Users\user\Desktop>pause
Press any key to continue . . .

As you can see the command echo %random% keeps producing relatively random numbers between 0 and 32,767 as expected.

At the same time using %random% to set a value for variable rnumber does not. It produces a not-so random number (possibly too between 0 and 32,767) but it is not random. If I were to guess right now it seems to be slowly growing in the 0 to 32,767 direction.

To clarify the script keeps producing a random number with line 2 on each execution (20160, 13887, 18885...), but line 1 seems to produce a number that keeps increasing with each execution of the batch file (28955, 29072, 29183, and so on in my multiple tests).

I already tried it on two different computers, Windows 7 x64 and Windows 2012 R2 respectively, running this 3 line script multiple times in row.

Next thing to try will be on a computer from a completely different network, I'm wondering if this has anything to do with domain policies, network, software..

What is going on here?

UPDATE:

When running the commands in sequence from the same CMD window it works as expected, but it does not when executing the same batch file multiple times.

• The line in the script echo %random% works as expected.
• The line SET rnumber=%random% does not.

(When executing the same script multiple times)