Coffee Math

According to the directions on the coffee can,  you use 1 to 1 1/2 tbsp (15 to 25 ml) of coffee for every 3/4 cup (175 ml) of fresh, cold water.  (Who the hell drinks coffee by the 3/4 cup anyway?)  My coffee/tea mug is 500 ml, Leaf's is 15 oz.  If I want 1 mug of coffee and Leaf wants two, how much coffee is needed? 

The reservoir of our coffee machine doesn't use oz or cups or ml.  It has marks labelled 2, 4, 6, 8.  Each little mark is about 300ml.  There are also plus a little travel mug (one or two) icon.  How much water is needed?

Perhaps a more important question...  Why does it take a calculator, an online metric-imperial converter, and 20 minutes to figure out how much coffee to put in the coffee machine?  I'm not math phobic by any means, I have very good numeracy skills.  Really though, should it be this difficult?  It sounds like a trick question from a grade nine math test.  I hate that only one country in the world officially uses the imperial system, and that they are our largest trading partner.

For the record, 8-12 tbsp of coffee, water just under the "10" mark in the machine.  Leaf says I make coffee too strong.