We don't know what system you have or if it's properly configured, therefore it's impossible to tell you why your memory scores are lower than you expect. Is your system identical to your firiend's?
i have 2gb pc2 6400 ram. my subscore is 4.7 but my friend also have 2gb of ram and have subscore of 5.3. so plz tell me about this low subscore
contact your RAM Manufacturer company. If Your RAM has made by small company than subscore will be low and if company is big like HP or Dell than subscore will be high.