Question Test/Service Menu Speaker not working?

Hi! I am currently running Wanamlite v3.4 (GT-i9500) and just a bit of curiosity I tried entering the Test/Service Menu. All of the tabs are working, then I noticed that nothing happens when I press Speaker, but when I try pressing the Speaker (R), a loud music plays. From my understanding, S4, both international versions have only 1 Loud Speaker. I can still hear the ringtones whenever someone calls or texts me, notifications and also perfectly functioning for both video and music playback, so that means the loud speaker works fine. Then I have read in another thread that S4 has 2 speakers, left and right, and the Speaker tab corresponds with the Left Speaker? It is quite confusing.

Hope someone can enlighten me on this. I hate bringing this to a Samsung Service Center.

Many thanks!