Speaker question - what 300 watts total power output and 40 watts RMS total means.?

looking to buying Akai 5.1 DVD Home theatre system (ADVD51) seen at : http://www.oo.com.au/Akai_5_1_DVD_Home_Theatre_Syst_P42023.cfm im wondering what 300 watts total power output and 40 watts RMS total means. for example does this mean that it can put out 300 watts but the speakers only put out 40 watts ?... show more looking to buying Akai 5.1 DVD Home theatre system (ADVD51)
seen at : http://www.oo.com.au/Akai_5_1_DVD_Home_Theatre_Syst_P42023.cfm

im wondering what 300 watts total power output and 40 watts RMS total means.
for example does this mean that it can put out 300 watts but the speakers only put out 40 watts ?
also, any ideas how loud do you think itll be for a room approx 4x4 meters ?

thanks .
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