@TMavica well. if you watching videos very often you can choose bigger size, it will be played smoothly. but with bigger size small files will use this minimum. for example if you choose 64KB all your 1-64KB files will reserve 64KB filesystem for each file. but small size is very rare for MyDocs partition, so you can experiment here
search files smaller 64kbytes. if none or not so many you can increase size to 128, 256 and test it again and again