Bit of an awkward way to phrase it, but basically:
Time in relativity is just one of four dimensions of space-time. Nothing really special about it. Yet the universe was once smaller than it is now and has evolved, changed, from a singularity till its size today.
But this implies that the whole of space-time (since you can't separate time from space) is evolving over time. Which time, then, is it evolving over? There's not supposed to be a global time for the universe, only time as perceived for an observer at a particular location.
So it seems very strange to me that the volume of the entire universe's space-time could change over time when time is part of the thing that's changing. It sounds like we're talking about two different kinds of time...