Python shared memory "buffer is too small for requested array"

I create 2 shared memory arrays with different sizes as below. The first one works but the second one results in error:

TypeError: buffer is too small for requested array

If I change the size from 224x224 to 300x300 it's fine. Why?

        ### first shm - ok###        fullFrame_bytes = 1280*720*3 # assuming RGB        self.fullFrame_buffer_shm = SharedMemory(name="cap_buffer", create=True, size=fullFrame_bytes)        # create buffer for getting results from the shm        fullFrame_shape = [720,1280,3] # needs to be rows, cols as per openCV        self.fullFrame_buffer = np.ndarray(fullFrame_shape, buffer=self.fullFrame_buffer_shm.buf, dtype=np.uint8)        ### second shm - not ok ###        segFrame_bytes = 224*224*4 # RGBA        self.segFrame_buffer_shm = SharedMemory(name="seg_buffer", create=True, size=segFrame_bytes)        # create buffer for getting results from the shm        segFrame_shape =  [224, 224, 4]         self.segFrame_buffer = np.ndarray(segFrame_shape, buffer=self.segFrame_buffer_shm.buf, dtype=np.uint8)