This preference dialog is activated through Edit/Preferences/Maximum Memory size
If your digital camera takes high-resolution photos (more than 2 Mega pixels), ClearBoard needs more memory for processing. This preference sets the maximum limit of memory ClearBoard can claim. If not enough memory is allocated, ClearBoard may appear to "hang" sometime when a high-resolution image is loaded. Usually, it is safe to set the maximum memory size to a very large value but smaller than the size of your machine's physical memory. For example, set maximum memory to 256 MB or above if your image size is higher than 4M pixels (2400x1800). ClearBoard only uses as much memory as it needs, which is less than 40 Mb for most of time.