Having both Latency and Buffer Size settings on Windows seems confusing at first as most people will assume that the latency is caused by the buffer size.
Latency refers to the how often the iD22 sends and receives its data. So if you set it to its lowest setting (Minimum), iD22 will transfer data to and from the computer every 1ms. Whereas if it is set to its maximum (Extra Safe) then it will do it every 32ms.
This is the reason why, depending on what latency you have iD22 set to, some of the buffer size options are greyed out. If you have the latency set to Extra safe (32ms), then setting a very small buffer size means that the buffer would fill up before it is time for iD22 to send/receive its next set of data, meaning that you would get lots of data going missing.
So when choosing the settings it is best to set it to something like a latency setting of "Low" and then work your way up the buffer sizes until you can get fully stable playback.