For a male age 19+ the 'normal' ranges are 13-77 mmol.
This equates to approximately 320-1200 of the american standard.
Us Aussies have the same scale. You are in the bottom end of normal, as are most men not undergoing puberty / not eating enough healthly fats / not getting adequate zinc etc. If you're really worried seek out a hormone replacement therapy doctor [which will be hard, they all seem to want to help menopausal women, but don't want a bar of us men]. Or just take ZMA, Alpha Male and eat plenty of healthy fats. Either way good luck.