I won't go into the technical Mumbo jumbo of that value ( as i hardly understand a word of that ) Mostly we noticed with the board that it wrongly detects the TRFC value, with 55 you are pretty sure it will work with any module... for 1GB modules you can tighten to eg 42. With 2gb dimms 55 and higher is sort of a must... but like I said before my templates proposed are guidelines and not specific required values. They have suited me well on this board and mostly you can run with a bit less, but that's for you to discover as each board/CPU/ram combo is different...

Hope it helps