%random% variable not returning a random number

I'm using this code:

set /a alg=!random!*!activecount!/32768+1

For the most part, it works. HOWEVER, the !random! variable isn't generating a completely random number. instead, it's constantly counting up at a slow pace. Now, assuming the variable !activecount! is equal to 2, it would constantly generate either 1 or 2, without changing, for a VERY long time. Why isn't the random variable randomizing? I tried echoing !random! after the fact, and it generates a random number then. What gives?