Alexander,
It's a little bit confusing, but just set up the PLL to output 1024 * 48 kHz = 49.152 MHz.
X = 2, N = 721, M = 1125, R = 3.
Then use the converter control registers to select 32 kHz instead of 48 kHz.
This gets you 32 kHz by using a clock divider instead of directly doing it with the PLL.