Time calculation in the main game loop.

[Mulligun911]

There is the code in the Quake 2 main game loop implementation:

if (!initialized)
{   // let base retain 16 bits of effectively random data
    base = timeGetTime() & 0xffff0000;
    initialized = true;
}
curtime = timeGetTime() - base;

I'm wondering about the line base = timeGetTime() & 0xffff0000. Why are they applying the 0xffff0000 mask on the retrieved time? Why not to use just:

if (!initialized)
{   // let base retain 16 bits of effectively random data
    initialTime = timeGetTime();
    initialized = true;
}
curtime = timeGetTime() - initialTime;

???
What is the role of that mask?